Why do some foreigners have "Mc" in their surname?

The mc in a person’s name means someone’s son or descendant. Can also write for Mac. It is said to come from Gaelic in Scotland and Ireland.

For example, a long time ago there was a man named Grady. He was handsome, graceful, young, rich in gold, brave and mighty, invincible, the most lonely master in the universe, invulnerable... In short, he was a big shot, and his son often mentioned me. He is the son of Grady, and my name is McGrady. Just like some people now say that I am the first generation descendant of Confucius, and I am the first generation descendant of his grandson.

So those with Mc in their surnames generally mean Ireland. Descendants of Scots.

The Rockets' Tracy McGrady is called McGrady. I don't know if it has anything to do with Ireland