The Celtiberians (or Celt-Iberians)The term Celtiberi appears in accounts by Diodorus, Appian and Martial who recognized a mixed Celt ic and Iberian people; Strabo saw the Celts as the more dominant group in this blend. were a Celtic people living in the Iberian Peninsula, chiefly in what is now north central Spain and northern Portugal, before and during the Roman Empire. The group originated when Celts migrated from what is now France and integrated with the local Iberian people. A sign that the two populations intermingled can be detected in the presence of Celtic elements among the names of Celtiberian nobility.