When Eiver called his son "Peleg" (divided), how did he know that the world would be divided in his (Peleg's) lifetime?
Seforno, Hadar Zekenim: The word "Peleg" also hints at the fact that, as a result of the sin of the Dor ha'Palagah, the people's life-span was cut in half. No one born after him lived 300 years (Da'as Zekenim).
Moshav Zekenim: What is the proof that Eiver was a Navi? Perhaps it was the Torah that called him Peleg (like we find in the Gemara, "Why was she called Rus?...")! He answers that if this were the case, others of that generation could have been called Peleg.
Rashi writes: "We learn that Eiver was a prophet, for he named his son for a future event." We can easily calculate that Eiver far outlived his son Peleg (11: 17-19). Perhaps he gave his son this name only after the event took place?
Gur Aryeh: It is unreasonable to assume that one would give a person a new name posthumously.
The Seder Olam informs us that the division of the world took place at the end of Peleg's lifetime. Why must this have been the case?
Rashi: We cannot say that the Dispersal occurred at the time of Peleg's birth, for the verse (11:1) implies that all 70 nations were already in existence, and Yoktan and his 13 sons had yet to be born. Nor did it occur in the middle of Peleg's life, for then the Torah would not be clarifying the date of the Dispersion.
Rashi writes: "'Niflegah ha'Aretz' - The languages were mixed up... and they were dispersed all over the world." Why does Rashi add the mixing of the languages here?
Gur Aryeh: "Niflegah" would literally mean that the nations decided to parcel out the earth among themselves. Rashi therefore clarifies that it was due to the differing languages that they spread out from the valley and dispersed over the earth.
Rashi writes: "Yoktan - he was humble and belittled himself." Why does Rashi expound on this name in particular?
Gur Aryeh: When we find that the name of a person has a clear meaning, we may assume that he would not be so named unless there was a connection to that meaning. 1
רש"י: נתבלבלו הלשונות: בפסוק כתוב שהארץ נפלגה, ומנין שהלשונות נתבלבלו?
גור אריה: משמע שהיה מעשה שגרם להם לחלוק את הארץ, ולכן פירש רש"י שזה משום בלבול הלשונות.
רש"י: ואם תאמר באמצע ימיו וכו': משמעות דברי רש"י שאם באמצע ימיו נפלגה הארץ אין ראיה שהיה נביא, וקשה למה הדבר כך?
גור אריה: באמצע ימיו אפשר שלא היה נביא אלא החלו לקרוא לו פלג בשעת המאורע, אבל אם הדבר היה במותו- אין לומר שקראו לו שם במותו, אלא מתחילה נקרא כך כי היה אביו נביא.
רש"י: ויקטן - שהיה עניו ומקטין עצמו: למה פירש רש"י את שמו?
גור אריה: כיון של'יקטן' יש משמעות, אין לקרוא כך לאדם אם הוא לא שייך לאותו ענין.