The apellaia (ἀπελλαῖα) were the offerings made at the initiation of a young man (kouros) at a meeting of a family-group (φρατρία phratria) of the northwest Greeks. Apellaios (Ἀπελλαῖος) is the month of these rites and oferrings, and Apellon (Ἀπέλλων, Doric form of Apollo), is the megistos kouros ("The great Kouros"). 
The brotherhood, the phratry, controlled the access to civic rights. There was a three-day family-festival, with initiation ceremonies, not concerning the state. The father introduced his young child, then again as a child (ephebos) who would become a grown-up kouros, and the husband his wife after the marriage. The three-day festival of the northwest Greeks was called Apellai, and was similar with the Ionic Apaturia. The three relative offerings of Apellai at least in Delphi were paideia (for child), apellaia (youth), and gamela (marriage; gamos in Greek).
According to Plutarch: "It was a custom for those who from children were initiated to grown-up kouroi, to go to Delphi and offer there the hair of their head to the god (Apollo). Theseus went there, and he only shaved the forepart of his head." "Apollo is the unshorn Phoibos." A similar offering was made in the Apaturia, which was called koureion (from κείρω keiro, "cut, esp. hair"). and corresponds to apellaion (ἀπελλαῖoν)
- Jane Ellen Harrison (2010): Themis: A study to the Social origins of Greek Religion, Cambridge University Press. pp. 439–441 ISBN 1108009492
- Walter Burkert (1985), Greek Religion. Harvard University Press, p. 255
- Plutarch Vit. Thes.v: Jane Ellen Harrison (2010): Themis: A study to the Social origins of Greek Religion, Cambridge University Press. p. 441 ISBN 1108009492
- Martin Nilsson, Die Geschichte der Griechische Religion, vol. I (C. H. Beck), 1955, pp. 137, 556