Green’s Dictionary of Slang

(US) silly, crazy.

1921		W.S. Walkley Three Golden Days 95: ‘Of course!’ she laughed [...] ‘What a goony I am!’ .
1939		in Merrie Melodies [animated cartoon] I’m so goony, loony tuney [HDAS].
1946		H.A. Smith Rhubarb 42: Don’t be a square. Don’t be goony.
1955		Mad mag. Jan. 5: You sure are goony, boy!
1965		R.L. Pike Mute Witness (1997) 156: A goony little bellhop.
1972		M. Rodgers Freaky Friday 16: A big, gooney smile all over his dumb face.
1974		(con. 1945) E. Thompson Tattoo (1977) 382: Water soaked the men’s uniforms [...] and streamed down their utterly foreign young faces with those high, goony haircuts.