Green’s Dictionary of Slang

1. to put someone in a position of sharing accommodation, esp. in a prison cell.

1732		Proceedings at Sessions (City of London) July 171/1: The Prisoner had been my Chum in the Fleet-Prison [...] I had desired the Chamberlain to let me be removed, but the House was then so full that I could not be chum’d elsewhere.
1825		Examiner 18 Dec. 4/2: There were other prisoners without a chum, who ought to have been chummed before me.
1836–7		Dickens Pickwick Papers (1999) 542: You’ll be chummed on somebody to-morrow.
1838		J. Grant Sketches in London 52: When a prisoner is first confined within the walls, he is entitled to what is termed a ‘chum ticket,’ which is a small piece of paper on which one of the officers of the prison, called the chum-master, writes the name of the party, with the number of the room in which he is to be ‘chummed’.
1857		T. Hughes Tom Brown’s School-Days (1896) 84: You’ll be chummed with some fellow on Monday, and you can sit here till then.
1859		C, Mackay Life & Liberty in America I 28: ‘Bunk together?’ ‘Yes; bunk, sleep, chum, live together’.
1871		L.H. Bagg Four Years at Yale 43: Chum, a roommate or particular friend [...] Chum is used also as a verb.
1885		A. Griffiths Fast and Loose III 208: You’ll have to chum with Devas here now that Dellew’s gone.
1901		T.B. Reed Master of Shell 11: By the way, who am I stuck with this term? I don’t want to get chummed again with that young ass Simson.
1917		‘Henry Handel Richardson’ Aus. Felix (1971) 4: They had chummed together on the seventy-odd-mile from Melbourne; had boiled a common billy and slept side by side.
1933		J. Spenser Limey 267: I was sorry ‘Spud’ had decided to chum with Castillo, but I suppose he thought I should be a dull cell mate.

2. (also chum in, chum it, chum up) to live with, to befriend.

1730		Wesley in Works (1831) VI 597: There are... some honest fellows in College, who would be willing to chum in one of them .
1762		C. Churchill Ghost Bk II n.p.: Old Maids and Rakes are join’d together. Cowuettes and Prudes, like April weather, Wits forc’d to chum with Common Sense [F&H].
c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: We Chumm’d together.
1822		‘A. Burton’ My Cousin in the Army 163: A worthy—he and I for years Have ‘chumm’d’ together.
1846		Swell’s Night Guide 68: She vent macadamizing again, and then she chummed vith a gonniff, and they took a crib and did the fence and bawdykin dodge.
1858		A. Mayhew Paved with Gold 252: It was resolved among these boys that they should ‘chum’ together.
1861		T. Hughes Tom Brown at Oxford (1880) 57: Then we fell in with a bird with mahogany tops, and, as usual, Drysdale began chumming with him.
1871		M. Clarke in Money Knocking About in N.Z. viii: This is the sort of young gentleman who [...] camps affably with the savages, ‘chums in’ with diggers.
1883		‘’Arry at the Royal Evening Fête’ in Punch 28 July 38/1: Ten bob and snap togs took me in, and I chummed with the very eleet.
1885		C.F. Lummis letter 28 Jan. in Byrkit Letters from the Southwest (1989) 267: These fellows that promise to chum it with us may peter out, but you and I stick together.
1885		L. Emanuel Jottings [...] of a Bengal ‘qui hye’ 126: A friend [...] with whom he’d ‘chummed’ for many eventful months.
1890		Bulletin (Sydney) 26 July 9/1: Our Gracious has been chumming in with the somewhat disreputable ex-Queen Isabella at Windsor.
1895		H.B. Norris [perf. Vesta Tilley] The Piccadilly Johnny with the little glass eye 🎵 The set of boys I chum with are the best-known set down town.
1898		West Australian (Perth) 5 Feb. 9/3: He was now Bob Edwards, the unkempt tramp, humping his bluey along the Sunset Track [...] and chumming with the human flotsam and jetsam that is for ever floating about these out skirting fringes of civilisation.
1903		A. Adams Log Of A Cowboy 357: These old pioneers naturally hung together and visited and chummed with one another.
1912		A. Wright Rung In (1931) 262: So you two have chummed up.
1912		Truth (Wellington) 6 Apr. 7/5: She chummed up with Abingdon Baird, a sport who owned a string of racers.
1919		Marvel 3 Mar. 15: He must be a bit of an ass [...] to chum in with Donbrook and Elthorne, who only soap him for what they can get out of him.
1928		C. McKay Home to Harlem 126: The two grades, cooks and waiters, never chummed together, except for gambling.
1932		J. Dixon Free To Love 131: Is Danny chumming with Neil Neilson?
1935		‘George Orwell’ Clergyman’s Daughter (1986) 91: You can chum in at our bin - four to a bin’s the best picking.
1940		Western Mail (Perth) 30 May 2/3: He chummed up with a Tommy batman over a few pints.
1951		S. Lewis World So Wide 164: Born here in Florry, but lived in England, and chummed with the Yankee troops here.
1986		S. King It (1987) 142: Not the people I chummed with.
2001		S. King Dreamcatcher 155: If you tell anybody I did this [...] I’ll never chum with you guys again.

3. (also chum in) to join in with, to accompany.

1865		Leaves from Diary of Celebrated Burglar 28/2: We ‘officed’ the other ‘gun’ to ‘chum in’ with us and have some ‘max’.
1891		East & Sth Devon Advertiser 12 Sept. 3/4: Never go chumming with an Apache.
1909		W. Irwin Confessions of a Con Man 152: We chummed down to the station.
2001		I. Welsh Glue 96: Spud jist chummed ays, eh explains.
2009		L. McIlvanney All the Colours 294: Moir chummed me down in the lift.
2021		A. Parks April Dead 89: ‘Just about to go there now. Fancy chumming me along?’.

4. to keep a lookout for someone.

2012

J. Fagan Panopticon (2013) 205: ‘I need tae pee but’ [...] ‘Ill chum you.’ Tash and Isla wander of to the [...] shribs.