Were the Celts Scottish or Irish?

The ancient Celts weren't Irish. They weren't Scottish, either. In fact, they were a collection of people/clans from Europe that are identified by their language and cultural similarities.

Where did the Celts come from originally?

The Celts were a collection of tribes with origins in central Europe that shared a similar language, religious beliefs, traditions and culture.

Were the Celts who came from Ireland?

From as far back as the 16th century, historians taught that the Irish are the descendants of the Celts, an Iron Age people who originated in the middle of Europe and invaded Ireland somewhere between 1000 B.C. and 500 B.C. That story has inspired innumerable references linking the Irish with Celtic culture.