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1620s, insomnie, from Latin insomnia "want of sleep," from insomnis "sleepless," from in- "not" (see in- (1)) + somnus "sleep" (see Somnus). The modern form is from 1758.
insomnia in·som·ni·a (ĭn-sŏm'nē-ə)n. Chronic inability to fall asleep or remain asleep for an adequate length of time.
A persistent and prolonged inability to sleep.