Kommentar zu Bereschit 11:29

יסכה JISCAH — This was Sarah; she was also named Jiscah (from a root meaning “”to see”, “to look”) because she could see the future by holy inspiration, and because everybody looked (gazed) at her beauty (Megillah 14a). The name Jiscah also has reference to princely dignity (נסיכות) just as the name Sarah (שרה) has an allusion to “ruling’’(שררה).

ויקח ארם ונחור, the singular mode here where we would have expected a plural mode, seeing that each of the brothers took himself a wife, is similar to the singular mode used by the Torah in Exodus 7,10 ויבא משה ואהרן, “Moses and Aaron came,” where we would have expected the plural mode, seeing that two people came. The Torah mentioned the names of the wives in honour of Avram. G’d changed Sarai’s name to Sarah. Seeing that Rivkah was the granddaughter of Milkah and became the wife of Yitzchok they were deserving of mention by name.

This was Sarah. You might ask: How does Rashi know this? Furthermore: What does it matter that Yiskah is Sarah? The answer is: Rashi knows this because before it is written that Haran was “the father of Milkah and Yiskah,” and it lists Haran’s [female] offspring. If so, why does it not mention Sarah as well, who was a daughter of Haran? Perforce, Yiskah is Sarah. Furthermore, Sarah is בג"ץ in the alef beis ofא"ת ב"ש , [in which א equals ת, and ב equals ש, etc]. And בג"ץ has the same numerical value as יסכה. Rashi offers three explanations for the name Yiskah because [the name hints to all of them, so] which one should be ruled out? Alternatively, it is because Sanhedrin 69b mentions two of them. And Rashi added a third, “princely”, because he is answering the question: Why was she not called by her actual name, שרי? It must be that יסכה means “princely,” and is thus similar to שרי, which means “ruling”. (source unknown)