Green’s Dictionary of Slang

(US) old fool, old fogey.

1911		Variety 16 Sept. 8/2: The organization of vaudeville agents [...] would [...] become known as ‘theatrical brokers’... Many agents familiarly known as the ‘A. K.'s’ (alter kokers)..would be classed by themselves.
1954		N. Mailer letter 12 June in Selected Letters (2014) 169: Amigo, I’m fraid we’re a couple of alta kakes.
1966		Trimble 5000 Adult Sex Words and Phrases.
1971		B. Malamud Tenants (1972) 143: Are you hiding on me or really balling it now you got started again? You young bloods have got it all over us alter cockers.
1986		J.A. Friedman Tales of Times Square 42: Mendela, you alter cocker.
1989		H. Rawson Dict. of Invective (1991) 276: old cocker (or gaffer or fart). An old man, especially a silly or senile one; often as alter kocker.
1995		Hartford Courant (CT) 12 Feb. G4/1: A bunch of old ‘alter kackers’ [...] hanging out and kvetching.
2009		J. Stahl Pain Killers 10: If you were an alta kocker in a jail cell, wouldn’t you want to be somebody else?
2009		Gazette (Montreal) 9 June 4/2: At the St Laurent Deli [the] 73-year-old aitress [...] calls him alter cocker [...] She calls all old men alter cocker.
2015		J. Stahl OG Dad 94: The alta kockers at my local Y, the old lions whose ear hair could scrape the rust off pieplates.