migraine

Migraine entered English around 1425 as a respelling, following French, of the Middle English megrim, itself from Old French migraigne. That traces back through Vulgar Latin to Latin hemicrania, 'pain in one half of the head,' from Ancient Greek hēmikranía — hēmi- ('half') plus kraníon ('skull').

The word's form shifted as it passed from Greek into Latin, then into Old French and Middle English as megrim, before being respelled migraine to match the French version around 1425.

It's cognate with megrim and hemicrania, and shares its kraníon root with cranium — the skull itself.