Douglas Harper's Etymology Dictionary
narco-
word-forming element meaning "stupor, narcosis, sleep," from Latinized form of Greek narko-, comb. form of narke "numbness" (see narcotic (n.)).
Wiktionary
narco-
pre. 1 Pertaining to stupor, sleep, or a state of unconsciousness. 2 Of or pertaining to narcotics or their trade and use.