The place-name Llanddeiniolen (first recorded in the form Landeynyolen in 1284) has been taken to suggest that Deiniol's son was the patron here. Deiniolen, or Deiniol fab, seems to have been regarded as a separate saint by the sixteenth century. It is possible that the diminutive suffix en might originally have distinguished 'little Llandeiniol' as distinct from Bangor, the major church of Deiniol.

Browne Willis notes a feast day on 22 November, which differs from the usual date for Deiniol in September.