Green’s Dictionary of Slang

1. a hump on a person’s back; thus him and his boy, a hunchback [the hunchback is seen as carrying a small child].

1873

Sl. Dict. 95: Boy, a hump on a man’s back. In low circles it is usual to speak of a humpbacked man as two persons – ‘him and his boy’.

2. champagne [allegedly f. Edward VII’s habit of merely saying ‘Boy!’ to an attendant page who automatically brought him a glass of that wine; note Binstead, A Pink ’Un and a Pelican (1898) (the context is 1879): ‘The young bucks of the present day, by the way, generally allude to a bottle of champagne erroneously as “the Boy,” in evident ignorance of the origin of the term, which is as follows: At a shooting party of His Royal Highness’s, the guns were followed at a distance by a lad who wheeled a barrow-load of champagne, packed in ice. The weather was intensely close and muggy, and whenever anybody felt inclined for a drink he called out “Boy!” to the youth in attendance; the frequency with which this happened leading to the adoption of the term. It does not follow, however, that everybody who uses the word nowadays was out shooting that day with the Prince.’].

1882		‘The fine young London Gentleman’ in Punch LXXXII 69/2: He’ll nothing drink but B. and S., and big magnums of the boy.
1884		Nat. Police Gaz. (NY) 2 Feb. 2/4: The Prince of Wales refers to champagne as ‘the boy’. He would probably speak of Jersey Lightning as ‘the old man eloquent’.
1890		Sporting Times 1 Mar. 1/4: The principal witness in the case of the British ‘boy’ which was lately before the courts was Mr. Corke. [...] The defender of home-made champagne was Mr. Goldberg.
1890		Dead Bird (Sydney) 31 May 2/3: To drink herself silly / With creme de chantilly / And a magnum or two of ‘The Boy!’.
1901		D. Cotsford Society Snapshots 74: What’s the matter, Daddles? — feel queer? . . . Nothing wrong with the ‘boy,’ is it?
1905		Illus. Police News 30 Dec. 6/4: To each dear little joy, you stand magnums of ‘Boy,’ / Which is slang, you must know, for champagne.
1905		Sporting Times 4 Feb. 1/1: One of the infernal nuisances of getting old is giving up champagne. But it is an old story—the old man is beaten by the boy.
1912		E. Pugh Harry The Cockney 274: We opened the ball, as a rule, with a pint of the ‘boy’.

3. the penis.

1896

Sheaves from an Old Escritoire 70: [She] gave me a shy little kiss [...] Oh! delightful! it made the boy still more proud; in fact he began to throb with delight [...] Still holding my boy she pulled the foreskin backwards and forwards a few times.

4. in homosexual senses.

5. in drug uses.