1868, from French hypnagogique, from Greek hypnos "sleep" (see somnolence) + agogos "leading" (from PIE root *ag- "to drive, draw out or forth, move"). Etymologically, "inducing sleep," but used mostly with a sense "pertaining to the state of consciousness when falling asleep." Related: Hypnagogically.
hypervigilance
hypha
hyphen
hyphenate
hyphenation
hypnagogic
hypno-
hypnobate
hypnopedia
hypnophobia
hypnopompic