Green’s Dictionary of Slang

chicken-brained adj.

stupid.

1678		Otway Friendship in Fashion III i: What a damn’d Chicken-brain’d Fellow am I grown?
1912		Bulletin (Sydney) 5 Sept. 47/2: They will drag a joke 90 miles over the hills, and toil at it for weeks, [...] for the poor two-minutes’ gratification they can get out of exploding it under some chicken-brained, dribble-chinned drifter, who [...] hasn’t wit enough to even discover that anything unusual has gone off in his vicinity of late.
1940		Western Daily Press 30 Apr. 3/6: The [...] chicken-brained foil for the star. Rollicking fun — but not for prudes.
1969		Portis & Roberts True Grit [film script] We’ll breed them for deer-hunting. They’re small and chicken-brained!
1971		M.G. Hindus Traveler in Two Worlds 65: Ye tell one more lie and, by Jesus, I’ll crack your goddam chicken-brained head.
1987		P. Lively Moon Tiger 91: And I have to admit that like that chicken-brained Camilla with whom I shared a flat I too had a sexual field-day.
2004		review at Amazon.com 🌐 His hulking barbarian servant Condo, who has a long thick eyebrow and a hook for his left hand that Solon once calls a ‘chicken-brained biological disaster.’.