Green’s Dictionary of Slang

1. (US) a fool, a simpleton, also as nickname.

1899		Oxford Register *KS) 26 May n.p.: The article [...] marks the editor of that paper a ‘tater head’ if nothing worse.
1928		Birmingham News (AL) 4 Dec. 22/4: The seniors graduationg are [...] ‘Shorty’ Reed, Miller Corin [...] and ‘Tater Head’ Johnson.
1934		Newton Record (MS) 27 Sept. 8/3: Coach Tater Head’ Johnson was unanimously elected sponsor of the class.
1941		Tennessean (Nashville, TN) 14 July 6/5: Folks, meet tater Head. That’s what all the fellows call him. [...] he doesn’t mind.
1952		(con. 1948) G. Mandel Flee the Angry Strangers 243: Don’t stay around’n push junk on kids for this potatohead.
1981		H. Gould Fort Apache, The Bronx 180: Don’t go gettin’ ethnic with me, potato head, or I’ll slap the shit outta you ...
1985		Hartford Courant (CT) Sports pt 2 22 Nov. D9/3: He won’t have to work too hard at it this season, with his memphis Connection [...] Steve ‘Tater Head’ Mitchell [...] and Archie ‘Caboose’.
1989		(con. 1960s) M. Kingston Tripmaster Monkey 317: Let me educate you, Mr. and Mrs. Potato Head, on what isn’t funny.
1991		D. Simon Homicide (1993) 463: You little Irish potatohead.
1995		C. Dubowski Toy Story 1: At the other end of the street stood the outlaw—Mr Potato Head—with a goof grin on his face.
2003		Spokesman-Review (Spokane, WA) 28 Mar. 25/4: He identified himself as a ‘tater head’ who is awed by the courage of George W. Bush.
2017		Rocky Mountain Telegram (NC) 1 Mar. 8/1: That group of guys gave coach Drake the nickname ‘Coach Tater Head’.

2. see potato-eater under potato n.