Green’s Dictionary of Slang

a chimney sweep or his assistant.

1832		in Egan Bk of Sports 400: But where the ‘chummy’ struck his man / ’Twas plain he left a trace, / And soon the baker (’twas a fact!) / Grew black about the face.
1836		‘The Vocal Chimbly Sweepery’ in Flash Casket 81: I’m called sooty Dick by the wulgar about, / I’m a chummy vot lives near saint Gilesis.
1846		Swell’s Night Guide 74: Tickets to be had at the bar [...] and at chummy’s over the way [...] No gentleman can dance in queer crabs, or hob-nail’d trampers.
1853		Bell’s Life in Sydney 181 June 2/6: According to the usages of society (what society, whether the Chummy Society, or the Drapers’ Society, witness did not state].
1859		‘The Awkward Squad’ 🎵 Our ensign was a chummy, but he made a sweep of that.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor II 369/2: A sweeper accompanied by a ‘chummy’ (once a common name for the climbing-boy, being a corruption of chimney), was depicted on his way to a red brick house, from the chimneys of which bright yellow flames were streaming.
1866		Wild Boys of London I 132/1: ‘Didn’t the chummy collar?’ ‘Didn’t he? Lor, how he sung out when the big peeler scurfed him.’.
1877		‘The New London Cries’ in Laughing Songster 109: The chummy so black, sir, with bag on his back.
1886		Sporting Times 30 Jan. 1/2: A youth of eleven summers should address this dusky foreigner [...] with the comprehensive and vigorous remark — ‘Hello chummy, wheres your muzzle?’.
1896		Mirror of Life 11 Nov. 3/3: [T]he chummies who made the first day of May famous as their annual outing only carried small brushes.
1922		Joyce Ulysses 159: On his annual bend, M’Coy said. They drink in order to say or do something or cherchez la femme. Up in the Coombe with chummies and streetwalkers and then the rest of the year as sober as a judge.