Green’s Dictionary of Slang

1. (US) unwelcome, esp. as at a bar.

[1933		W. Winchell On Broadway 24 May [synd. col.] A Hollywood soda-jerker forwards this glossary of soda-fountain lingo out there… ‘Shoot one’ and ‘draw one’ is one coke and one coffee… [...] ‘Eighty-six’ means all out of it].
1942		Wash. Post 5 Apr. TC1/5: ‘Eighty-six means out,’ I said. ‘“The tuna-fish salad is 86” means there isn’t any more. And if you say a guy is 86, that means he’s fired or all washed up or something like that.’.
1963		M. Braly Shake Him Till He Rattles (1964) 85: Even if Carver did street him, Bear would be eighty-six all over town.
1982		G.V. Higgins Patriot Game (1985) 200: The boss was even gonna throw you out, permanent eighty-six, you didn’t stop doin’ this.

2. (US) dead.

1986

J. Ellroy Suicide Hill 254: ‘If this joker Klein is eighty-six, how you gonna make him for the heists?’.