- insanity (n.)
- 1580s, "state of being insane," from Latin insanitatem (nominative insanitas) "unhealthfulness," noun of quality from insanus (see insane). Meaning "extreme folly" is from 1844.
- 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.