English
headcase
From head + case.
Proto-Indo-European *kap- ‘head’
…
Proto-Germanic *haubudą ‘head’
Proto-West Germanic *haubud
Old English hēafod ‘head’
Middle English heed ‘head’
English head
Proto-Indo-European *ḱh₂d- ‘to fall’
…
Latin cadō ‘to fall’
Latin cāsus ‘a fall; accident, chance’
Old French cas ‘an event’
Middle English cas
English case
Today it means
noun A mentally unbalanced, unpredictable person, especially one who displays aggressive behavior.
Language periods are conventional ranges, not dates for this word.
Etymograph / headcase