The cromlech could be responsible for the name of the village. ‘Maenorbyr’ may well take its name from the same root as Ynys Byr (Caldey Island) just around the coast. It’s thought this could be ‘pure island’ (used in the same sense as many islands are called Holy Island). Ynys Byr has a long history of sacred use, from the Neolithic through Bronze Age up to the monks who live there to the present day. In the same way, Maenorbyr replaces Ynys (’island’) with ‘maen’ (’stone’); holy or sacred stone.
Pyro was one of the early Celtic Christian abbots of the first Celtic Christian community on Caldey/Ynys Pyr. The lives of various Celtic "saints" imply that Maenor (Manor) Bier (Pyro) was given to Pyro by the local post-Roman Celtic warlord and that there was a very early small medieval settlement near the church (but possibly pre-dating the church). The actual headland sticking out into the sea is called Priest's Nose and the area between the church and the actual headland is called Parson's Piece. It's clear to me that the whole area has been associated with holiness and spirituality for a very long time indeed.