Longman Dictionary of Contemporary English
Douglas Harper's Etymology Dictionary
also harebrained, 1550s, from hare-brain "giddy or reckless person" (1540s), probably from hare, on notion of "flighty, skittish."
Wiktionary
a. (alternative form of harebrained English) alt. (alternative form of harebrained English)
Usage examples of "hare-brained".
I could have been safe at home, pleasuring myself groggy with Elspeth and sponging off her skinflint father, facing nothing worse than the prospect of bear-leading her family in Society, and here I was imprisoned in a lonely castle with five dangerous lunatics bent on dragooning me into a hare-brained adventure that was certain to put my head in a noose.
There, he had been privileged to lend his aid to his dazzling friend in various hare-brained exploits.
And so you see, Enoch, I am well accustomed to others devising hare-brained plans for how I am to live.
Whole sections had been taken over by the King’s pack of semi-feral spaniels, who’d become inbred even by Royal standards and thus hare-brained even by Spaniel standards.
I didn't even dare think of the risks of their hare-brained impersonation scheme, but on the other hand I couldn't contemplate the alternative if I refused.
I suppose to approach the thing in any other way would have been useless, for it would have been constant admission of the imposture, and what an idiot, hare-brained scheme it was.