AnnaS asks: What is the Gaelic word for Celtic?

In modern Scottish it is Gaidhealach for the race and Gàidhlig for the language. In neither of those words is the dh pronounced anything at all like a dental plosive or stop. If heard at all it would be something of a y sound. What the word was back when the Scots still lived in Hibernia when the Romans (who still pronounced all Cs hard anyway and who first met the Celts much earlier in the Gauls) I have no idea.

There were also Goidelic Celts (Scots and Irish) and Brythonic Celts (Britons and Gauls) and the terms above would only refer, at least in modern Gaelic, probably only to the Goidelic.