1877 (adj.); 1879 (n.), from insomnia. Earlier was insomnious (1650s).
Entries linking to insomniac
insomnia n.
"chronic inability to sleep," 1620s, insomnie, from Latin insomnia "want of sleep, sleeplessness," from insomnis "sleepless," from in- "not" (see in- (1)) + somnus "sleep" (from PIE root *swep- "to sleep"). The re-Latinized form is from 1758.