Didn’t the ancient Druids believe in a messianic child that would lead them?
The ‘child of promise’ is quite common in many mythic systems and can be found in some examples of Celtic mythic material. There is a common confusion of the more general ‘child of promise’ mythic motif and the very specific Middle Eastern ‘messianic’ but there is no evidence of a ‘messianic’ motif in Celtic cosmic religion.