(Ἑκαέργος), a surname of Apollo, of the same meaning as Hecaerge in the case of Artemis. (Hom. Il. 1.147.) Here too tradition has metamorphosed the attribute of the god into a distinct being, for Servius (Serv. ad Aen. 11.532, 858) speaks of one Hacaergus as a teacher and priest of Apollo and Artemis.
[L.S]A Dictionary of Greek and Roman biography and mythology
Smith, William
A Dictionary of Greek and Roman biography and mythology. William Smith, LLD, ed. 1890