To Eber were born two sons: the name of the one was Peleg, for in his days the earth was divided, and his brother's name was Joktan.
Genesis 10:25

Strong says Peleg means "earthquake", but that seems extremely unlikely. It is the same spelling and pronunciation as a Hebrew word for "stream", which is a natural division in the land. The verse itself seems to define Peleg's name, by using the word for "divided", which is palag, spelled the same but pronounced differently. The scholarly consensus seems to be that his name means "division" and that makes the most sense in context as well.