(Ἀμφιετής), or AMPHIE'TERUS, a surname of Dionysus. (Orph. Hymn. 52. 1, 51. 10.) It is believed that at Athens, where the Dionysiac festivals were held annually, the name signified yearly, while at Thebes, where they were celebrated every third year, it was interpretated to be synonymous with τριετής.
[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