σεληνιάζω (< σελήνη), act, in Manetho (Caren., 4, 81), in NT depon. -ομαι, to be moonstruck, i.e. epileptic (epilepsy being supposed to be influenced by the moon): Refs Mat.4:24 17:15.† (AS)
Thayer:
1) to be moon-struck or lunatic 2) to be epileptic 2a) epilepsy being supposed to return and increase with the increase of the moon. This meaning is doubtful as the Greeks knew nothing of epilepsy.
σεληνιάζομαι
selēniazomai
sel-ay-nee-ad'-zom-ahee
Middle or passive voice from a presumed derivative of G4582; to bemoonstruck, that is, crazy