Peleg born: “the earth was divided”
Eber named his son Peleg (“division”), because in his days the earth was divided.
To Eber were born two sons. The name of the one was Peleg, for in his days the earth was divided. His brother’s name was Joktan.
Genesis 10:25 (World English Bible)
Peleg's name marks a turning point. Most conservative interpreters connect the “division” with the scattering of nations and languages at Babel, described in the next chapter.
Dating notes
Ussher suggested Noah divided the lands among his descendants around Peleg's birth, and that the rebellion at Babel followed a few years later. The birth year itself is derived directly from the Genesis 11 ages.