From Greek 'hemikrania' (half-skull pain) — dramatically worn down through Latin and French, literally 'half-head.'
A severe, recurrent headache, typically affecting one side of the head, often accompanied by nausea, visual disturbances, and sensitivity to light and sound.
From Old French 'migraigne,' from Late Latin 'hēmicrānia,' from Greek 'hēmikrānia' (pain on one side of the head), from 'hēmi-' (half) and 'krānion' (skull, upper part of the head). The word was dramatically shortened as it passed through Vulgar Latin and Old French — the entire first syllable 'hēmi-' was worn down to 'mi-.' Greek 'krānion' comes from PIE *ḱerh₂- (head, horn), the same root that gave English
The word 'migraine' is what happens when Greek 'hēmikrānia' (half-skull) is worn down by centuries of mispronunciation. The 'hēmi-' (half) was eroded to 'mi-,' and 'krānia' (skull) became '-graine' — so thoroughly transformed that the connection to 'half' and 'cranium' is invisible without etymological excavation. Galen wrote extensively about hemicrania in the 2nd century CE, making it one of the oldest documented neurological conditions