英语词源字典 - 在线词源网站

insanity (n.)[insanity 词源字典]: 1580s, "state of being insane," from Latin insanitatem (nominative insanitas) "unhealthfulness," noun of quality from insanus (see insane). Meaning "extreme folly" is from 1844.[insanity etymology, insanity origin, 英语词源]
sanity (n.): early 15c., "healthy condition," from Middle French sanité "health," from Latin sanitatem (nominative sanitas) "health, sanity," from sanus "healthy; sane" (see sane). Meaning "soundness of mind" first attested c. 1600.