New Orleans was famous for its oyster loaf in the 19th century. When husbands came home late in New Orleans, they were sure to bring with them a “peacemaker” or “la mediatrice”—an oyster loaf—to a waiting spouse.
 
The “peacemaker” dish became popular throughout the South. The oyster loaf (oysters in a hollowed-out loaf of bread) has a long history; “peacemaker” is cited in print from at least 1873. Some scholars believe that the New Orleans oyster loaf or “peacemaker” helped to create the famous New Orleans oyster “po’ boy” sandwich.
 
The long list of the names of sandwiches served on long rolls includes blimpie, bomber, Cuban (medianoche), Dagwood, garibaldi, gondola, grinder, hero, hoagie, Italian,  jawbreaker, muffuletta, pilgrim, pistolette, po’ boy (poor boy), rocket, skyscraper, spiedie, spucky (spuckie, spukie), submarine (sub), torpedo, torta (Mexican po’ boy), wedge and zeppelin (zep).
 
   
(Oxford English Dictionary) 
oyster loaf n.
(a) a loaf or roll of bread having a crust stuffed with oysters (obs.);
(b) U.S. regional (chiefly Louisiana) a baked sandwich consisting of a hollowed-out loaf of bread filled with oysters and other ingredients (cf. POOR BOY n., PO’ BOY n.); (also) the bread for such a sandwich.
eOE Bald’s Leechbk. (Royal) II. xxiii. 210 Ore wætan [read hwætene] mete gearwa & cocnunga ealle sint to forbeodanne, & eal a wætan ing & a smerewigan & *osterhlafas & eall swete ing.
1747 H. GLASSE Art of Cookery ix. 99 To make Oyster-Loaves.
1837 B. DISRAELI Venetia I. iv, A dish of oyster loaves.
1888 Forest & Stream 16 Feb. 64 Cold baked chicken, oyster loaf (and boiled duck if desired after the first day) were the chief articles of diet that this crew fed on during the trip.
1986 B. FUSSELL

II. viii. 113 Only plentitude can account for the number of oyster dishes named by New Orleans restaurant cooks desperate to distinguish their bivalves from the po’ boy oyster loaves of the bars.
 
What’s Cooking America
A predecessor was the Peacemaker Sandwich (La Mediatrice), a loaf of French bread, split and buttered and filled with fried oysters. The poetic name derives from the fact that 19th-century husbands, coming in late from a carouse or spree, would carry one home to cushion a possible rough reception from the lady of the house.
 
1838 - The first recorded American recipe for Oyster Loaves was in Mrs. Mary Randolph’s cookbook called The Virginia Housewife or Methodical Cook. This cookbook is considered the first truly American cookbook and the first regional American cookbook cookbook:
To Make Oyster Loaves—Take little round loaves, cut off the top, scrape out all the crumbs, then out the oysters into a stew pan with the crumbs that came out of the loaves, a little water, and a good lump of butter; stew them together ten or fifteen minutes, then put in a spoonful of good cream, fill your loaves, lay the bit of crust carefully on again, set them in the oven to crisp. Three are enough for a side dish.

1901 - The Picayune’s Creole Cook Book, 2nd edition, by the Picayune newspaper, also contained a recipe for Oyster Loaf:
Oyster Loaf - La Mediatrice
Delicate French Loaves of Bread
2 Dozen Oyster to a Loaf
1 Tablespoon of Melted Butter
 
This is called the “famous peacemaker” in New Orleans. Every husband who is detained down town, laughingly carried home an oyster loaf, or Mediatrice, to make “peace” with his anxiously waiting wife. Right justly is the Oyster Loaf called the “Peace-maker,” for, well made, it is enough to bring the smiles to the face of the most disheartened wife.
 
Take delicate French loaves of bread and cup off, lengthwise, the upper portion. Dip the crumbs out of the center of eaah piece, leaving the sides and bottom like a square box. Brush each corner of the box and the bottom with melted butter, and place in a quick oven to brown. Fill with broiled or creamed oysters. Cover with each other and serve.
 
23 November 1873, New Orleans (LA) Times Picayune, “Not a Peacemaker,” pg. 8:
He dropped in to get for his watching lady a dozen fried oysters in a loaf, put up in one of those square boxes, and styled by rascally old husbands peace-makers. 
 
24 May 1891, Syracuse (NY) Herald, pg. 3, col. 6:
Oyster Loaves.
N. Y. Sun.
New Orleans is famous for many dishes peculiar to itself. it should be famous for its oyster loaves. You see them advertised everywhere in the streets. An oyster loaf is half of a ten-cent double-polated loaf of white bread. It is split down on one side and then a part of the soft interior is taken out and all the rest is toasted. After that a dozen fried oysters are put in the loaf and it is closed and has a wedge of toasted bread fitted into its open end. The oyster loaf is said to be an amazing peacemaker for married men on lodge nights.
 
20 July 1893, Kansas City (MO) Star, pg. 7:
CARRIES HOME AN OYSTER LOAF.
How a New Orleans Man Saves a Certain
Lecture After Being Out Late.
From the New York World.
When the New Orleans man returns from making a night of it “with the boys” he provides himself with what is known as a peacemaker, and carries it home under his arm. The peacemaker is also known as an oyster loaf, and it is the chief product of certain hostelries called oyster saloons. A box-shaped loaf of bread is taken—one that has a thick, firm crust—and the top crust is cut off so as to form a cover. Then the inside is hollowed out with a knife made for that purpose until a wall of the snowy interior remains about half an inch in thickness. It is done so neatly that the pastry box looks as if it had been lined with white velvet. Into this piping hot fried oysters are packed until the loaf is full, and then the cover is tied up with a white ribbon. When this whole has been wrapped in paper, the buyer flees as a bird to his home. The little difficulty with the key hole overcome, he steps into the awful presence undismayed. There she stands, grim as of yore, but without an apologetic word the erring one climbs slowly up the stair and holds forth the peacemaker. She takes it, puts down the lamp and removes the cover. The deliciously flavored steam ascends like sweet incense until it reaches her rigid nostrils and then her stern features relax into something like a smile. While her lord is hanging his shoes on the chandelier and depositing his hat carefully in the wash basin, she sits on the side of the bed eating the spoils of domestic war. There are no promises to go unfulfilled and become the cause of future bitterness. With all thus turned on the waves of life’s troubled sea the matrimonial bark sails bravely on.
 
2 January 1894, Grand Forks (ND) Daily Herald, pg. 3:
The oyster fry in a box as a peacemaker was a popular joke half a dozen years ago; now they put ice-cream in boxes, and all sorts of things.
 
14 November 1900, Arizona Republican (Phoenix, AZ), pg. 7, col. 4 ad:
If you are out late and know your wife will be cross when you get home, stop in at
CLARK’S
and have an oyster loaf put up and take it home with you. You will find it a good peacemaker. We deliver them anywhere up to midnight.
 
12 February 1905, Montgomery (AL) Advertiser, pg. 7 ad:
At the eleventh hour Oyster Loaves—Peacemakers served with care.
(Harrison’s Cafe - -ed.)
 
10 October 1913, Wilkes-Barre (PA Times Leader, pg. 10:
Oyster Peacemakers.
Four or five large potatoes, one egg, white bread crumbs, two dozen large oysters, one heaping tablespoonful of butter, one tablespoonful flour, 1/2 cupful cream, 1/2 cupful oyster liquor, seasoning of salt and pepper, and mix shrimps for each “peacemaker.” Wash and peel the potatoes, then rewash and trim them to even sized oval shapes. Scoop out the centers so as to leave a neat case. Parboil these cases until the potato is just getting tender, but do not completely cook them on any account. Take them out of the water, dry on soft cloth, brush each over with beaten egg, and roll in bread crumbs. Bake this in a quick oven until crumbs are a light brown; or, if in haste, the potatoes may be fried in smoking hot fat. To make filling:  Blend the butter and flour in saucepan, add the oyster liquor and cream; stir until it boils, then add bread crumbs sufficient to make sauce of good creamy consistency. Then season mixture with great care. Cut oysters in halves; beat without boiling them in sauce, then pile up in potato cases. Put six shrimps on top of each, and serve the “peacemakers” very hot, garnished with parsley.
 
30 January 1940, Lowell (MA) Sun, pg. 16, col. 2:
We read of a husband, detained downtown, “carrying home la mediatrice, that celebrated peacemaker of new Orleans, the delicious oysterloaf, filled with broiled or creamed oysters, and warranted to bring a smile to the face of the most disheartened wife.” Thus the artists of the kitchen become negotiators of treaties of domestic peace. That’s genuine “home cooking.” 
 
12 January 1947, Washington (DC) Post, “From Old New Orleans,” pg. S2:
“LA MEDIATRICE”
(For Four)
2 dozen oysters
2 egg yolks, beaten
Salt and pepper
Fat
1 loaf French bread
Flour
 
Dip oyster in flour. Brush them over with beaten egg yolk, which has been seasoned with salt and pepper. Now fry in hot fat for three or four minutes, until a delicate golden brown. Drain on absorbent paper. Have ready a loaf of French bread, having removed the top and the soft inside part, thus forming acase. Put a little oyster liquor into this case and set it in the oven to get thoroughly hot. Place the oysters in the loaf, garnish with a few slices of gherkins, cover with the lid, and serve hot.
 
9 September 1949, Chicago (IL) Daily Tribune, “FOR MEN ONLY!; Some Oyster Lore, Then the Creole Husband’s Secret for Making Peace with His Irate Spouse” by Morrison Wood, pg. A7:
One of the most delicious oyster concoctions I know of is oyster loaf. But I much prefer the Creole designation of this dish, which is la mediatrice, meaning peacemaker. It is really a gastronomical masterpiece—fried oysters served in a hollowed-out loaf of bread,
 
It apparently received its Creole name from two sources, as far as I can determine. When Louisiana parents came home from a party in the small hours, they expected their children to be worried and fretful. So they’d bring them a loaf of bread filled with fried oysters.
 
However, the version I prefer has it that the lord and master of the household, coming home at or near dawn with a load aboard, or as the English put it “high tiddley-eye-tie,” would present his irate wife with la mediatrice, which he had somehow managed to pick up on the way home. I have never tried this as a pacifier, but it sounds like a good gag.

Use Entire Loaf of Bread
Cut off the top of the entire loaf of French bread and scoop out the inside to make a basket, leaving about 1/2 inch of crust all around. Then dip 2 dozen oysters in flour. In the meantime, beat the yolk of one egg, and season it with salt and freshly ground pepper to taste, and mix in a teaspoon of sherry. Now dip the floured oysters in the seasoned egg yolk, then in yellow corn meal. Fry them in hot fat until brown. Remove them from the fat, drain, and then place the drained fried oysters in the loaf of bread, which previously has been toasted. Lay thin slivers of dill pickles over the oysters, place the lid on the loaf, and pop it into the oven to become thoroly (sic) warm.
 
5 November 1954, Dallas (TX) Morning News, “There are Many Ways to Prepare Oysters,” part 5, pg. 5:
The Oyster Loaf is a unique preparation and illustrates what amounted to a custom. Oysters have ever been popular in restaurants where businessmen gather. Many men returning home from the business sections wished they could take some oyster dish with them.
 
Some unknown solved this demand with a package which not only made a heat insulator to keep the oysters warm but also lent a perfect background to the oysters. The taking home of oyster loaves followed naturally. In one area the oyster loaf became known as a “peacemaker.” No doubt it was taken home by a tardy husband on occasion to appease a waiting wife.
(...)
OYSTER LOAF
Ingredients: One loaf bread, creamed oysters (recipe and amount below), sliced lemon, melted butter, parsley.
Method: Cut top from loaf of bread, remove center crumbs, leaving a rim of one inch. Brush loaf and top slice with melted butter inside and outside. Fill loaf with creamed oysters, cover with top crust and bake in a moderate oven, 375 degrees F., ten minutes or until thoroughly heated. Serve on a platter and garnish with slices of lemon, dipped in parsley. Fried oysters may be used as the filling instead of creamed oysters.
 
CREAMED OYSTERS
Ingredients: One pint oysters, 1/2 cup butter, 1/2 cup flour, 3 cups milk, 1 teaspoon salt, 1/3 teaspoon pepper.
Method: Simmer oysters in their liquor about 5 minutes or until edges begin to curl. Drain. Melt butter in top of double boiler, blend in flour, add milk and cook until thick, stirring constantly. Add oysters, seasonings, and heat. Serve in patty shells or on toast. Serves six.
 
19 September 1958, Chicago (IL) Daily Tribune, “Old New Orleans Gives Us This Tasty Oyster Loaf” by Morrison Wood, pg. B4:
Errant husbands, returning home in the wee hours [and perhaps with a guilty conscience] would stop for that same toothsome delicacy and present it as a peace offering to irate wives. It was aptly named “la mediatrice” [the Peacemaker].
 
“La mediatrice” of the Creoles is a refined version of an 18th century English recipe for oyster loaves and is a most savory concoction for late evening or early morning snacks. Cut off the top… (Same as 1949 article above—ed.)
 
2 September 1976, Dallas (TX) Morning News, “Oyster Orgy Is Closest Thing to a Bacchanal,” section E, pg. 16:
THE PEACE MAKER
Slice a loaf of Italian bread lengthwise and remove the soft crumb to form a shell with the crust.
 
In a skillet, fry eight slices of bacon until crisp. Remove and drain. Sprinkle one half-pint of drained, shucked oysters with flour and fry individually in bacon fat until brown on both sides. Remove and keep warm. Slice two medium tomatoes and cook in remaining bacon fat until heated through. Remove and sprinkle with salt and pepper.
 
Layer the bacon, tomatoes and oysters in the bread shell, wrap in aluminum foil and bake at 350 F. until heated through, about 15 or 20 minutes. Cut the loaf diagonally into slices. Mix a half cup of sour cream and a teaspoon of horseradish into a sauce and use as a spread. Serves four. Guaranteed to leave you in a benign frame of mind, at peace with the world.
 
30 September 1987, Globe and Mail (Toronto, Canada), “Oysters! Aw, Shucks!” by Joie Warner, pg. C11:
PEACEMAKER OYSTER PO BOY
According to Jane and Michael Stern in their book Real American Food, the culinary legend of the oyster “po boy” is that it was once known as la mediatrice, because it was what dallying husbands brought back to assuage their wives.