The story
From bird + brain, implying that birds, having small brains, are unintelligent (although this is untrue for many birds).
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: Someone who is not intelligent. Full definition →
From bird + brain, implying that birds, having small brains, are unintelligent (although this is untrue for many birds).
Etymology from Wiktionary, CC BY-SA 4.0.