Green’s Dictionary of Slang

1. a brothel-keeper, a bawd.

1761

Memoirs of [...] Jane D****s 74: Alkl the gentlemen that frequent our house, allow me to be the fairest dealer in Covent-garden.

2. (US Und.) a wholesaler of counterfeit money.

1822		Tom And Jerry; Musical Extravaganza 53: Dealers in queer, passers of bad bills.
1872		G.P. Burnham Memoirs of the US Secret Service 92: He soon made up his mind that the dealer in the ‘queer’ rather than the ‘shover’ was the party who piled his gains with the greatest ease.
1924		G. Henderson Keys to Crookdom 402: Dealer. Wholesaler of bogus currency.

3. (drugs, also deal, John Deal) a drug seller, one with a wholesale role, as opposed to the less important pusher n. (3c)

1928		Phila. Eve. Bulletin 5 Oct. 40/4: Here are a few more terms and definitions from the ‘Racket’ vocabulary: [...] ‘pusher,’ a ‘small-time guy’ who sells for a large dealer.
1936		D. Maurer ‘Argot of the Und. Narcotic Addict’ Pt 1 in AS XI:2 120/2: dealer. A peddler. Often restricted to a druggist who is amenable to persuasion.
1949		Monteleone Criminal Sl. (rev. edn).
1959		A. Salkey Quality of Violence (1978) 160: She knew nothing about [...] the business transactions between himself and the ganja dealers.
1961		T. Taylor Baron’s Court All Change (2011) 31: He’s a dealer [...] He sells it’ [i.e. cannabis].
1971		H.E. Roberts Third Ear n.p.: deal n. [...] 2. one who sells drugs (John Deal).
1984		C. White Life and Times of Little Richard 149: All the hookers, hustlers, and dealers hung around there.
1998		G. Burn Happy Like Murderers 241: The runaways and misfits coming round and the dealers, and with the dealers the busts and the Bill.
2000		Indep. 10 Jan. 6: The drugs would come to us [...] you just had to give a local dealer a call and he’d drop it off.
2010		K. Richards Life 203: To be a dealer you’ve got to be way in front, otherwise you slip up.