Green’s Dictionary of Slang

a fool, usu. as a term of derog. address.

1904		R. McCardell Show Girl and Her Friends 62: I don’t care if a lot of people say Dopey is a dead one.
1908		Eve. World (NY) 18 Jan. 8/3: Not that poor Dopey don’t have his troubles.
1921		N&Q 12 Ser. IX 466: Dopey. Fool; inefficient soldier.
1929		S. Ornitz Haunch Paunch and Jowl 218: I knew that Dopie Ikey could not withstand the cajolery [...] ‘Chief,’ I said, ‘one of these boys is weak-minded, nothing more than an idiot’.
1930		J. Lait Gangster Girl 106: ‘Huh, a dopey,’ contemptuously spat the gang chieftain.
1938		J. Curtis They Drive by Night 237: Now, dopey, you take a ball of chalk.
1941		G. Kersh They Die with Their Boots Clean 4: Are you listening to me, you Dopey, over there? Give him a poke in the eye, somebody — he’s going to sleep.
1955		B. Schulberg On the Waterfront (1964) 130: Don’t ya recognize him, dopey? That’s old man Doyle.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 199: A person who is ‘wanting in the upper storey’ is [...] a dopey dick.
1967		L. Bruce Essential Lenny Bruce 259: I wouldn’t really do it, dopey.
1967		P. Thomas Down These Mean Streets (1970) 13: What’s it mean? [...] You gotta ask, dopey? [Ibid.] 20: ‘Hey, whatta ya think you’re doing?’ I shouted. [...] ‘Whatta ya think, mopey?’.
1974		G.F. Newman You Flash Bastard 126: ‘We should have eaten afterwards,’ Sneed said casually. ‘Why?’ [...] ‘You’d have been lighter, dopey.’.
1989		P. Benchley Lush 105: This isn’t sex, dopey. It’s friendship.
2004		R.G. Barrett Rosa Marie’s Baby (2013) [ebook] ‘ sure ain’t talking to you, dopey’.
2007		B. Reed ‘The Meat Axe by the Kitchen Door’ in Passing Strange (2015) 3: ‘It’s Wednesday, not Sunday, dopey’.