- tranquility
- late 14c., from O.Fr. tranquilite (12c.), from L. tranquillitatem (nom. tranquillitas) "tranquilness," from tranquillus "tranquil," perhaps from trans- "over" (here in sense of "exceedingly") + a root related to quies "rest" (see quiet). Tranquilize formed in Eng. 1620s; tranquilizer "sedative" is from 1824 (first reference is to ground ivy); in reference to one of a large group of anti-anxiety drugs, it is first recorded 1956.