“Hump Day” is a day that gets people “over the hump” (over 50% completion of something). The “hump day” of the seven-day week is Wednesday. The term “hump day” has been cited in print since the 1950s. “Hump day” now almost exclusively means Wednesday, but the earliest uses in 1955 and in 1956 had other meanings.
 
“Hump Day” has been printed on many images, usually featuring a camel.
     
[This entry was assisted by research from Garson O’Toole of the Quote Investigator.]
 
 
Wiktionary: hump day
Etymology
The term alludes to the fact that Wednesday is the middle of the work week, meaning that one has made it “over the hump” towards the weekend.
Noun
hump day (plural hump days)
1. (informal) Wednesday.
 
Newspapers.com
10 June 1955, Oklahoma City (OK) Star, All-Church Press sec., pg. 1, col. 3:
SUMMER HUMP DAY
Sunday, June 19, has been designated as “Summer Hump Day”. The slogan is, “Let’s go over the hump and beat the slump.” This day will be to re-emphasize and vitalize both attendance and stewardship. It will be similar to last year’s “High Peak Day.”
 
24 February 1956, Cincinnati (OH) Post, “End of ‘Seventh Week’ Time To Be Merry” by Rosalie Pere, pg. 28, col. 6:
Over the Hump
 
The co-ops work up to seventh week from the day of registration, talking about it, worrying about it and forcing social calendars toward an arrangement which allows the upmost of studying at the end of sixth week.
 
THE ORDEAL of a school section is so strenuous that many co-ops celebrate “hump day”. They are over the hump at noon Wednesday of fourth week.
 
29 March 1956, Houston (TX) Post, “Post Card” by George Fuermann, pg. 1, col. 1:
HAVEN’T SEEN YOU IN A MONTH OF HUMP DAYS—The Weather Eye, Conoco’s paper, has a note on the enrichment of the language which we share with all working people. First, you may recall “TGIF” from school days—“Thank God it’s Friday.”

“Hump Day” is the newer key to hope, being the name for Wednesday,
 
Newspapers..com
24 February 1957, The Idaho Sunday Statesman (Boise, ID), “About Town,” sec. 2, pg. 12, col. 2:
Steve Fouchek has been suffering from spring fever since last December….finally has found a cure.
 
“Hump day,” he calls it. This is the way it works: Wednesday, coming in the middle of the week, is a hump day…for if you an live until Wednesday, you’ve got it almost made…and it’s downhill sailing until the week end. The trick is to celebrate every “hump day eve.”
   
Newspapers.com
17 September 1957, Corpus Christi (TX) Times, “Signs Prove It: Fun Spices School Job” by Margaret Ramage, pg. 1-B, col. 1:
A sleepy camel with a huge hump is the “insignia” on the yellowish-green Wednesday poster, above the caption: “This is Hump Day, nothing more,—and still the week is just half o’er.”
 
Newspapers.com
18 June 1958, Oroville (CA) Mercury, “Frightening Thing” by Harriet Helman Gray, pg. 14, col. 5:
Wednesday used to be the happy-hump-day of your week. On Wednesday you crossed the divide between one weekend and the next.
 
Newspapers.com
23 May 1963, The Bulletin (Bend, OR), “Sagebrushings” by Ila S. Grant, pg. 4, col. 7:
Odds and Ends
I was planning to write a little paragraph, last week, about Hump-day. That’s Wednesday. On Hump-day, you’re over the hump. The City Hall reporter here at The Bulletin gave me this piece of intelligence. the other day, Dick Fagan beat me to it, in his Oregon Journal column. He gave someone else the credit.
 
YouTube
GEICO Hump Day Camel Commercial Happier than a Camel on Wednesday
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Jun 4, 2013
 
YouTube
Tony Romo celebrates Hump Day with GEICO
CBS Sports
Feb 3, 2019