late 14c., "sudden fit of paralysis and dizziness," from Old French apoplexie or directly from Late Latin apoplexia, from Greek apoplexia, from apoplessein "to strike down and incapacitate," from apo- "off" (see apo-), in this case probably an intensive prefix, + plessein "hit" (cognates: plague, n., also with a root sense of "stricken"). The Latin translation, sideratio, means "disease caused by a constellation."