Green’s Dictionary of Slang

1. (US) an unpleasant person; also a term of address.

1856		N.O. Weekly Delta 23 Nov. p.1 in A.P. Hudson Humor of the Old Deep South (1936) n.p.: The lower rejin of Loozeana, to that sitty of unhearn-of wikkedness, frogs, katfish and Frenchmen, called Orleans.
1864		A.F. Hill Our Boys 93: You dare to raise that knife to that boy, and off goes your head, cat-fish!
1867		‘Johnny Cross’ ‘Sally Doe’ in Orig. Pontoon Songster 8: Sally Doe, the wife of Cat Fish Mick-i-e.
1902		Ade Girl Proposition 9: He could not believe that a real Diana would trifle with a blue Cat-Fish.
1919		A.C. Inman 28 Dec. diary in Aaron (1985) 165: I am a fool to waste my time about a catfish who is less than nothing to me.

2. US one who poses as someone that they are not, also as v. [‘The person who is catfishing puts the bait out there, and waits for someone to bite. The person who falls for the bait and believes the catfisher is the catfish’ comment on Urban Dict. 18 Nov. 2013].

2010		on Urban Dict. 2 Sept. 🌐 ‘Many guys have multiple accounts on facebook because they are catfishes’.
2014		C. Eble (ed.) UNC-CH Campus Sl. Spring 2014 3: CATFISH — someone who misrepresents himself or herself: ‘I thought I met a great guy online, but he turned out to be a catfish and was really a girl’.
2022		Twitter 27 Feb. 🌐 [R]ussian soldiers trying to match on tinder with women from the country they’re invading and then getting catfished for intel is such a weird ‘we live in the future’ moment.
2023		Byline Times Sept. 2/2: Wootton’s catfishing tactics, which he used to trick and bribe men into providing sexually compromising material.

3. US a promise or claim that turns out to be false.

2014

C. Eble (ed.) UNC-CH Campus Sl. Spring 2014 3: CATFISH [...] A phony claim: ‘Joe said he could get us into the show, but it turned out to be catfish’.