Insomnia is Latin for 'sleeplessness,' from in- (not) and somnus (sleep), from PIE *swep- (to sleep) — the same root that gave Greek hypnos and English somnolent.
Habitual inability to sleep; chronic sleeplessness.
From Latin insomnia, meaning 'want of sleep, sleeplessness,' from insomnis (sleepless), composed of in- (not) and somnus (sleep). The Latin somnus comes from PIE *swep-no-, from the root *swep- (to sleep), which also gives English somnolent, Somnus (the Roman god of sleep), and, through a different descendant, the Greek hypnos (sleep). Key roots: *swep- (Proto-Indo-European: "to sleep"), somnus (Latin: "sleep").