Green’s Dictionary of Slang

(US) a silly, amusing, eccentric or insane person.

1944		J.M. Inks diary Eight Bailed Out (1954) 29 July 48: ‘Dig this goofball,’ Griff said.
1955		B. Schulberg Waterfront (1966) 258: There’s no room for goof-balls in this business.
1965		W.C. Anderson Adam M-1 83: I seem to have a penchant for attracting the greatest collection of goof-balls.
1973		L. Bangs in Psychotic Reactions (1988) 130: The band themselves come on like total goofballs.
1984		W.M. Henderson Stark Raving Elvis 8: Byron [...] glared back at the goofball.
1995		P. Cornwell From Potter’s Field (1996) 186: Her dad died. You’re divorced. She’s got no brothers and her mother is in and out of bed with goofballs.
2003		Mad mag. Feb. 35: After allowing the liberal goofball two sentences O’Reilly spins lengthy, elaborate scenarios [etc.].
2015		L. Berney Long & Faraway Gone [ebook] What was the little goofball waiting for?
2021		J. Ellroy Widespread Panic 271: A kiddie korps sews Sir Guy shirts and sicknik silks for L.A. gang goofballs.