late 14c., "sudden fit of paralysis and dizziness," from L.L. apoplexia, from Gk. apoplexia, from apoplessein "to strike down and incapacitate," from apo- "off" (see apo-), in this case probably an intensive prefix, + plessein "hit" (cf. plague, also with a root sense of "stricken"). The L. translation, sideratio, means "disease caused by a constellation."