Green’s Dictionary of Slang

(US) comb. adj. to describe an enthusiasm or habit, e.g. car-whacky, car crazy.

1944		P. Kendall Dict. Service Sl. n.p.: victory girls . . . ’teen age girls who are khaki-wacky.
1944		D. Burley N.Y. Amsterdam News 15 Jan. 10A: A few of the chicks got rather wacky over some solid studs wearing Uncle’s khaki.
2021		T. Swerdlow Straight Dope [ebook] I’m [...] a little shack whacky as I haven’t left the house.