The dedication of the church to Deiniol in medieval times appears to be confirmed by the Welsh form of the place-name, Llanddinol, although the variant spellings of the name are not easy to reconcile. The place-name appears in several forms in the Book of Llandaff with the element diniul, diniuil, dineul. As an outlier from all other clusters of dedications to Deiniol, it seems unlikely that the church is dedicated to the same saint, but a connection cannot be ruled out, and may have become assumed over time.

It may be significant that Browne Willis omits any dedication for the church in his Parochiale Anglicanum (1733), although he does provide Deiniol in the dedications given in Thesaurus Rerum Ecclesiasticarum (1754).