A.messenger who brings out news from within: hence, one who betrays a secret, informer, “ἐ. γίγνεται ὡς . .” Th.8.51; “ἐ. γίγνεσθαί τινος” Pl.Lg.964e, etc.
II. on the Greek stage, messenger who told what was doing in the house or behind the scenes (opp. ἄγγελος, who told news from a distance); first used by Aeschylus, Philostr.VS1.9.