Didacus.

An exclusively Iberian name recorded from the mid-8th century, and frequently throughout the 9th century, predominantly in northwestern Iberia. Of unknown origin. Suggestions have included: a masculine derivation from Greek διδαχή (didakhḗ), perhaps by conflation with διάδοχος (diádokhos); an extension of Latin Didus, Didius (masculine form of Dido) with the Basque suffix -ko-; a Celtic *Divakos, from *deiwos "god"; derivation from Celtiberian Titiacus, from a presumed *Tritiakos. Vernacular forms Diaco, Diago by the 10th century, the form Diego is recorded from the late 11th century.