Goidelic was introduced in Ireland by the Gallaeci of Galicia, N.W. Spain circa 500 B.C. The Gallaeci spoke an archaic Goidelic Q-Celtic tongue called Gallaic. The Gallaeci are the Halstatt Celts that settled in Galicia circa 800 B.C. In Ireland, Gallaic evolved into Primitive Irish.
Celtiberian was introduced in N.E. Spain by the La Tene Celts that settled in the area circa 500 B.C. Celtiberian is also Q-Celtic, but not Goidelic.