(Ἑβδομαγέτης), a surname of Apollo, which was derived, according to some, from the fact of sacrifices being offered to him on the seventh of every month, the seventh of some month being looked upon as the god's birthday. Others connect the name with the fact that at the festivals of Apollo, the procession was led by seven boys and seven maidens. (Aeschyl. Sept. 804; Hdt. 6.57; Lobeck, Aglaoph. p. 434.)
[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