Goidelic is a "q" Celtic language and is archaic like Latin, Greek and Sanscrit.

It is found only on some 300 Ogham inscriptions dated to 300 - 500 CE.

Goidelic was introduced very early to the British Isles. Isolated in Ireland, it was not affected by the P-Celtic Britonnic that prevailed in great Britain. The language has three modern descendants one of which, Manx Gaelic, was allowed to become extinct in the 20th century.