Frank Richardson Kent (1877-1958) was a longtime political pundit on the Baltimore (MD) Sun, writing a syndicated colu,mn titled “The Great Game of Politics.” Kent popularized the term “fat cat” (sometimes given as “fat-cat” or “fatcat") in a 1925 column, a June 1928 American Mercury article titled “Fat Cats and Free Rides,” and in his 1928 book Political Behavior.

Wrote Kent in 1925: “It ought perhaps to be explained that Fat Cat is the significant and revealing name in political circles for the sleek, rich fellows who enter politics for one reason or another and depend for their standing and success upon the liberality with which they shell out the dollars.”

The term “fat cat” (used like the rhyming “bigwig") also exists outside of politics to describe anyone with money, such as a Hollywood “fatcat” or a “fatcat” record producer. “Fat cat” is a somewhat dated term, but is still used.


Wikipedia: Fat cat (term)
Fat cat is a political term originally describing a rich political donor, also called an angel or big money man.

The New York Times has described fat cats as symbols of “a deeply corrupt campaign finance system riddled with loopholes”, with Americans seeing them as recipients of the “perks of power”, but able to “buy access, influence policy and even veto appointments.”

It is also commonly used to describe a rich, greedy person who, due to ownership of large amounts of capital, is able to “live easy” off the work of others.

History
The word was first used in the 1920s in the United States to describe rich political donors.

The term’s coinage for political purposes has been attributed to Frank Kent, a writer for the Baltimore Sun whose essay “Fat Cats and Free Rides” appeared in the American Mercury, a magazine of commentary run by H. L. Mencken. Kent wrote:

“A Fat Cat is a man of large means and no political experience who having reached middle age, and success in business, and finding no further thrill ... of satisfaction in the mere piling up of more millions, develops a yearning for some sort of public honor and is willing to pay for it. The machine has what it seeks, public honor, and he has the money the machine needs. ”

The 1960 campaign for the Democratic nomination to the presidency was marked by competition between fellow Senators Hubert Humphrey and John F. Kennedy. Their first meeting was in the Wisconsin primary, where Kennedy’s well-organized and well-funded campaign defeated Humphrey’s energetic but poorly-funded effort. Humphrey objected to the media, “The Kennedy forces are waging a psychological blitz that I cannot match. I’m not the candidate of the fat cats....”.

A 1972 book by sociologist G. William Domhoff, titled Fat Cats and Democrats, contrasted the Democratic Party’s perceived populism with its funding structure. In Domhoff’s view, “Short of a nationwide system of public financing for candidates ... it seems likely that wealthy fat cats will find one way or another to finance the candidates of their choice.”

The campaign finance reforms following the Watergate scandal greatly reduced the amount of money that individuals could contribute to a political campaign. In the words of Ben J. Wattenberg, “The fat cats were driven from the temple....”

During a 1997 $1,000-per-plate dinner at the Hilton Washington for the Republican Party, which the New York Times dubbed “a lucrative display of the resilience of big-money campaign fund-raising”, street protesters calling for further reform dressed in “fat cat” costumes and chanted “Hey, hey, ho, ho! Corporate fat cats have to go!” In the 2008 Democratic race, a group of wealthy backers of Sen. Hillary Clinton wrote to Speaker of the House Nancy Pelosi, warning her they might withdraw financial support for the Democratic Congressional Campaign Committee if Pelosi did not change her position on whether the party’s superdelegates “should support the party’s pledged delegate leader”. According to the Center for Responsive Politics, the signers included donors such as Haim Saban and Robert L. Johnson, and had given the party nearly $24 million since 2000. In response, the grassroots liberal political action committee MoveOn called the move “the worst kind of insider politics—billionaires bullying our elected leaders into ignoring the will of the voters,” but reassured members that “when we all pool our resources, together we’re stronger than the fat cats.”

Use in culture and imagery
The word has since acquired a meaning of a rich, powerful person of possibly ‘undeserved’ wealth. It is now commonly used in editorial cartoons. In the British printed media, a fat cat is usually depicted as a cat-faced, clad in a pin striped suit corpulent middle-aged man holding or smoking a thick cigar representing a venal banker or a high earner executive or “captain of industry”.

Merriam-Webster’s Online Dictionary
Main Entry: fat cat
Function: noun
Date: 1928
1 a : a wealthy contributor to a political campaign fund b : a wealthy and privileged person c : big shot
2 : a lethargic complacent person
— fat–cat \ˈfat-ˌkat\ adjective

(Oxford English Dictionary)
fat cat slang (orig. and chiefly U.S.), a political backer; also transf.
1928 F. R. KENT Pol. Behavior vi. 59 These capitalists have what the organization needs—money to finance the campaign. Such men are known in political circles as ‘*Fat Cats’.
1949 Sat. Rev. Lit. 16 Apr. 4 Hollywood celebrities, literary fat cats.
1960 Economist 8 Oct. 157/2 Methods of exhorting [sic] money which..harry so-called ‘fat-cats’—rich supporters—to an extent which looks like cruelty to animals.
1966 New Statesman 21 Jan. 78/3 The kind of balance-sheet fat cats who characterise the worst side of ITV.
1971 Flying Apr. 34/1 Those who view the business jet as a smoke-belching, profit-eating chariot of the fatcat.

7 November 1925, Denton (MD) Journal, pg. 2, col. 1:
KENT ON THE REPUBLICAN FACTIONAL FIGHT.
The battle alignment in Maryland between the Weller and the anti-Weller forces in the Republican party promises the finest Fat Cat fight ever seen in this State, writes Frank R. Kent in last Sunday’s Baltimore Sun. Primaries of any sort are the politicians’ Paradise, but a primary in which there is a collection of Fat Cats on each side is almost too good to be true.

That is what this one looks to be, and the practical Republican workers, particularly those of darker hue, find it difficult to disguise their joy over the prospect.

It ought perhaps to be explained that Fat Cat is the significant and revealing name in political circles for the sleek, rich fellows who enter politics for one reason or another and depend for their standing and success upon the liberality with which they shell out the dollars.

When one of this type enters the ring, either as candidate or backer, the magic words “Fat Cat” ring throughout the wards, precincts and districts, and the “‘boys,” big and little, white and black, joyfully prepare to reap the harvest. At the race tracks the men who come out with $200 and more in their pockets, determined to bet but not knowing much about the horses, are also Fat Cats to the touts, but the phrase had its origin in politics, and it is there most aptly used.

The thing that so greatly stirs the enthusiasm of Republican workers over the prospective primary is that it is completely a grudge fight between the Republican Fat Cats—not between tow of them, but between two groups, a fight for revenge in which the rich men are lined up against one another in a battle for blood. Soon or late every Fat Cat in the party will likely be involved.

27 May 1928, Springfield (MA) Republican, pg. 7F, col. 7:
“FAT CATS” IN POLITICS
“Only reformers believe in the fundamental intelligence of the American people—politicians know better.” This is one of the assertions made by Frank R. Kent in the leading article for the June issue of the American Mercury, entitled “Fat Cats and Free Rides.” THe people don’t care how much corruption there is in government, except in a period of economic distress, when their envy is aroused, according to Mr. Kent. The politicians, says the American Mercury writer, know this, and bank on it. That is one reason why the Democratic bosses haven’t made a big fuss over the large campaign contributions of the Republicans.

A “fat cat” is “a man of large means and no previous political experience, who, having reached middle age, achieved success in business, and finding no further thrill, sense or satisfaction in the mere piling up of more millions, develops a yearning for some sort of public honor, and is willing to pay for it.”

The most prominent of the “fat cats” now holding high office, according to Mr. Kent, is Andrew W. mellon, secretary of the treasury. The fattest “fat cat” in the Senate—“and a splendid specimen he is,” says Mr. Kent—is Senator T. Coleman DuPont of Delaware. Senator Phipps of Colorado is also put into that class by Mr. Kent, and Senator James Couzens of Michigan is described as “fat cattish.”

Google Books
June 1928, American Mercury, pg. 129:
FAT CATS AND FREE RIDES
BY FRANK R. KENT

23 September 1928, Los Angeles (CA) Times, “Gossip of the Book World,” pg. C16:
“Fat Cats” flourish in American politics, according to Frank R. Rent in “Political Behavior” (Morrow.) He defines a “Fat Cat” as a man who, having reached middle age and achieved success in finance or business, yearns for public bonor and prestige.

4 November 1928, New York (NY) Times, “Miracle Regarded as Smith’s Big Need” by Frank R. Kent, pg. 55:
Instead of the fat cats of politics being all on the other side there is something like an even division.

OCLC WorldCat record
Fat-cat lobbyists make your laws.
Author: Robert Canfield
Publisher: New York, Vantage Press [1968]
Edition/Format: Book : English : [1st ed.]

OCLC WorldCat record
Fat cats and Democrats; the role of the big rich in the party of the common man
Author: G William Domhoff
Publisher: Englewood Cliffs, N.J., Prentice-Hall [1972]
Edition/Format: Book : English

OCLC WorldCat record
Fatcat
Author: Alan Bird; Beagle Bros.
Publisher: San Diego, Calif. : Beagle Bros., ©1984.
Edition/Format: Computer file : 5.25 in. disc : Program : English
Summary: Library program organizes all your DOS 3.3 and ProDos file names for sorting, searching, and printing.

OCLC WorldCat record
New Deal fat cats : business, labor, and campaign finance in the 1936 presidential election
Author: Michael J Webber
Publisher: New York : Fordham University Press, 2000.
Edition/Format: Book : English : 1st ed