Green’s Dictionary of Slang

congratulations, also as excl; thus synon. congraggers, congratters.

1884		L. Troubridge Life amongst Troubridges (1966) 167: Congrats on Ernest’s appointment to the Royal Yacht.
1906		‘O. Henry’ in Works 153: ‘Congrats,’ says I.
1910		‘Doss Chiderdoss’ ‘His Lincoln Form’ Sporting Times 12 Mar. 1/3: Please accept my congrats., Mrs. P.
1914		‘Ian Hay’ Lighter Side of School Life 95: ‘I’m to be a prefect next term.’ ‘Oh! Congratters!’.
1929		J.B. Priestley Good Companions 436: Congrats on the show, Miss Bant!
1932		Dundee Courier 29 Mar. 7/3: Air Ministry’s Congrats. The following message was sent to Mr Mollisoon [etc.].
1936		A.E. Duckett ‘Truckin ’round Brooklyn’ in N.Y. Age 11 July 7/2: The Y Spartans rate some orchids for their swing last week. Congrats girls.
1941		‘Digg Mee’ ‘Observation Post’ in N.Y. Age 14 June 9/4: I extend congrats from old digg mee.
1946		K. Amis letter 30 July in Leader (2000) 81: Congrats, old son.
1954		Picture Post 13 Nov. 8: Congrats! [...] and belated congratulations to the people responsible for the wonderfully clever ‘special effects’.
1962		T. Berger Reinhart in Love (1963) 84: Congrats, sir! King-size vol one reaches you in Friday’s mail.
1975		L. Rosten Dear ‘Herm’ 120: Wow, Leo, 1,000,000 clams! Congrats!
1988		D. Woodrell Muscle for the Wing 56: I guess congrats are in order.
1990		R. Doyle Snapper 53: Yeah, Sharon. Congrats, said Mary.
2005		P. Howard Curious Incident of the Dog in the Nightdress 57: ‘Congrats’ and ‘Oh my God, you were, like, so amazing.’.
2021		P Howard Braywatch 68: I believe congrats are in order.
2022		I. Fitzgerald Dirtbag, Massachusetts 166: ‘Congrats. You’re next’.