"inclined to sleep, drowsy," 1650s, from a Latin diminutive of somnus "sleep, drowsiness," from PIE *swep-no-, suffixed form of root *swep- "to sleep."
Entries linking to somniculous
*swep-
Proto-Indo-European root meaning "to sleep."
It forms all or part of: hypno-; hypnosis; hypnotic; hypnotism; insomnia; somni-; somnambulate; somniloquy; somnolence; somnolent; Somnus; sopor; soporific.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit svapnah, Avestan kvafna-, Greek hypnos, Latin somnus, Lithuanian sapnas, Old Church Slavonic sunu, Old Irish suan, Welsh hun "sleep;" Latin sopor "a deep sleep;" Old English swefn, Old Norse svefn "a dream."