- tranquility (n.)
- also tranquillity, late 14c., from Old French tranquilite (12c.), from Latin tranquillitatem (nominative tranquillitas) "tranquilness," from tranquillus "tranquil," perhaps from trans- "over" (here in its intensive sense of "exceedingly") + a root related to quies "rest" (see quiet (n.)).