Green’s Dictionary of Slang

chummy adj.

also chummy-chummy
[chum n.]

friendly.

[UK]Comic Almanack May 216: They grows asham’d of chummy friends, / And makes us hold our jaws.
Randolph Regulator (Asheboro, NC) 13 May 1/1: I found my friend Manson, an indivdual with whom I had been particularly chummy at college.
Star-Democrat (Easton, MD) 9 Mar. 1/5: He had no particular friends [...] and was not disposed to be what is known as chummy.
[UK]Sporting Times 15 Nov. 3/1: Two old boys of the cheeriest and chummiest type.
[US]St. Paul Globe (MN) 23 Feb. 9/2: Getting Chummy. Delegates Matthews and Gifford are getting quite chummy. They are together a great deal.
[US]Humboldt Union (KS) 26 Nov. 1/7: I meet a companiable man, in the interval we grow a trifle chummy [...] Well, very chummy.
[Aus]H. Lawson ‘Mitchell’s Jobs’ in Roderick (1972) 148: They put another boy that I was chummy with up there.
[UK]‘R. Andom’ Martha and I 72: Being of a chummy disposition, I walked over [...] to engage in a conversation.
[UK]‘Doss Chiderdoss’ ‘A Dangerous Dad’, Sporting Times 3 Feb. 1/4: The gal took no notice o’ me, in the least, / But she soon with the old ’un got chummy.
[US]H. Green Actors’ Boarding House (1906) 252: They were getting quite chummy.
[Aus]Sun. Times (Perth) 24 July 2nd sect. 11/3: The negro’s wife, a white woman, is said to insist on being chummy with the wife of her husband’s manager, which the latter refuses to allow.
[UK]A. Brazil Fourth Form Friendship 29: ‘You’ll be with Fifth Form girls, and you can’t expect them to be particularly chummy with you’.
[Ire]Joyce ‘The Boarding House’ Dubliners (1956) 60: They shared in common tastes and for this reason were very chummy with one another.
[UK]T. Norman Penny Showman 57: We got a bit chummy.
[US]N.Y. Tribune 23 July 2/2: Mrs Oboe and Mrs Ruff have become such good friends [...] and Mrs Ruff and Mrs Oboe will make all sorts of chummy plans.
[UK]E. Glyn Flirt and Flapper 56: Flirt: What do you call that indelicate handling, then—? Flapper: Oh! Just being chummy.
[US]‘Paul Cain’ ‘One, Two, Three’ in Penzler Pulp Fiction (2006) 3: I [...] spent the day [...] getting chummy with agents.
[US]E.S. Gardner Case of the Crooked Candle (1958) 46: Down to that chummy little restaurant on Ninth Street.
[US]M. Spillane Long Wait (1954) 138–9: Vera and Lenny Servo [...] were pretty chummy until Vera disappeared.
[UK]Wodehouse Jeeves and the Feudal Spirit 63: Our relations have always been chummy to the last drop.
[US]C. Himes Imabelle 18: She didn’t like to get chummy with folks.
[US]C. Himes Rage in Harlem (1969) 19: [as 1957].
[US]G.V. Higgins Friends of Eddie Coyle 18: One of the screws saw him getting chummy with the chaplain.
[UK]P. Theroux London Embassy 28: He said he knew ‘Eddie Pahang’. Very chummy.
[Aus]J. Byrell (con. 1959) Up the Cross 45: [G]iving Airboy a little chummy pat.
[Aus]R.G. Barrett White Shoes 79: She was very chummy.
[US]A. Rodriguez Spidertown (1994) 113: Sometimes the head man gets too chummy with the new boy and the old boys get jealous.
[US]J. Stahl Permanent Midnight 345: It was very chummy-chummy. We shook hands.
[UK]M. Collins Keepers of Truth 268: The guy was all chummy.
[Scot]L. McIlvanney All the Colours 229: [G]etting chummy with the South Belfast UVF.
[Aus]L. Redhead Thrill City [ebook] I did my best at chummy. ‘Even on death row they get a last meal’.

In derivatives

chumminess (n.)

friendliness.

[Ire]Dublin U. Mag. July 16/2: Myles was still the old brotherly friend; and Rosey, in spite of all her chumminess with Willy, was none the less affectionate to him.
[US]Tennessean (Nashville, TN) 24 Aug. 12/1: Do not imagine that I am making a false pretence of chumminess with the millionaire.
Good Words Mag. 26 469: They had been class-fellows these two years, and a considerable chumminess had sprung up between them, yet they were not on terms of social equality.
[US]Sun (NY) 24 Nov. 6/5: A continual confabbing and a truly charming chumminess between his Grace the Dude [sic] of Somerset and my friend McGinty.
[US]Brownsville Dly Herald 25 Aug. n.p.: Secretaries hitchcock and Wilson are the chums of the cabinet [...] it is regarded as quite natural that they should become intimate to chumminess.
[UK]Wodehouse ‘Pillingshot’s Paper’ in Captain Feb. 🌐 Scott might have his faults, yes, but this chumminess was certainly complimentary.
[UK]Liverpool Echo 8 Feb. 3/5: ‘Pals in the Army’ This splendid sketch gives a true insight into that ‘chumminess’ which is one of the secrets of our Army’s wonderful morale.
[UK]Wodehouse Carry on, Jeeves 35: You can’t call a chap the world’s greatest authority on the yellow-billed cuckoo without rousing a certain disposition towards chumminess in him.
[UK]Derby Dly Teleg. 8 Dec. 4/6: Their waggish attempt at chumminess only has the effect of making my daughter furious.
[Scot]Aberdeen Jrnl 15 Feb. 2/3: Mrs Buck [has] failed to appreciate the natural ‘chumminess’ of the British fighting man.
[Scot]Aberdeen Eve. Exp. 27 Oct. 2/3: Cheek by jowl in cheerful chumminess sit the Labour leaders all.