O.E. dælere, agent noun from deal. Meaning "player who passes out the cards in a game" is from c.1600; meaning "one who deals in merchandise" is from 1610s. Illegal drug sense is recorded by 1920. Related: Dealership (1916).
A person who makes a living from gambling, whether or not an actual dealer-out of cards •Dealer, ''player who distributes the cards,'' is attested from 1600: A bookmaker, who is known as a dealer in refined usage(1950s+ Gambling)
A person involved actively and aggressively in a range of negotiations, trades, purchases, etc; wheeler-dealer(1950s+)
A person who sells narcotics; peddler; connection, pusher: The ''dealer'' (not ''pusher'') is the man who sells all this(1920s+ Narcotics)