English
headslapper
From head + slapper.
Proto-Indo-European *kap- ‘head’
…
Proto-Germanic *haubudą ‘head’
Proto-West Germanic *haubud
Old English hēafod ‘head’
Middle English heed ‘head’
English head
Today it means
noun A mistake of obvious stupidity.
Language periods are conventional ranges, not dates for this word.
Etymograph / headslapper