- somnolence
- late 14c., from O.Fr. sompnolence, from L. somnolentia "sleepiness," from somnolentus, from somnus "sleep," from PIE *swep-no, from base *swep- "sleep" (cf. Skt. svapnah, Avestan kvafna-, Gk. hypnos, Lith. sapnas, O.C.S. sunu, O.Ir. suan, Welsh hun "sleep," L. sopor "a deep sleep," O.E. swefn, O.N. svefn "a dream").