The Welsh form of the place-name are first attested in the first half of the twelfth century.

As an outlier from all other clusters of dedications to Deiniol in the north and west, it seems unlikely that the church, from which the place-name is derived, was originally dedicated to the same saint. The different spelling is suggestive of a different individual, although a connection with the patron of Bangor cannot be ruled out, and may have become assumed over time.