Charles Ellicott Commentary Genesis 10:25

"And unto Eber were born two sons: The name of the one was Peleg. For in his days was the earth divided. And his brother`s name was Joktan." — Genesis 10:25 (ASV)

Peleg; for in his days was the earth divided.—This may refer to the breaking up of the descendants of Shem into separate nations, each occupying a distinct region. Thus, while Joktan took Arabia and, in time, expelled the Hamites from that country, Asshur, Aram, and Peleg occupied the regions to the north and northwest.

However, since Peleg, according to the Tôldôth Shem, was born only 101 years after the flood, Noah’s family could scarcely have multiplied to as many as 500 people in such a short time; and Mr. Cyril Graham considers that the name refers to “the first cutting of some of those canals which are found in such numbers between the Tigris and the Euphrates.” This interpretation is made more probable by the fact that Peleg in Hebrew means water-course.