Omiyamairi ((the custom of) taking one's baby to a shrine) was originally one of the initiation rituals in which a baby was taken to the tutelary to ask the permission to become a member of the local community.
子供のお宮参りの本来はこの氏神にお参りして、その土地の一員になることを認めてもらうための儀式の一つだった。