English
madbrained
From mad + brained.
Proto-Indo-European *meyth₂- ‘to change’
…
Proto-Germanic *maidijaną ‘to change’
Old English *mǣdan
Old English ġemǣdan
Middle English mad
English mad
Today it means
adj madcap; crazy
Language periods are conventional ranges, not dates for this word.
Etymograph / madbrained