At the end of Parshat Noach (Breisheet 11:29-30) we read about Avraham’s family: “Avram and Nachor married. The name of Avram’s wife was Sarai, the name of Nachor’s wife was Milkah, the daughter of Haran, who was the father of Milkah and Yiscah. Sarai was barren, she had no child.”
Why is Yiscah mentioned here? Who was she and why don’t we hear about her again?
According to Rashi, who brings Rabbi Yitzchak’s interpretation from the Talmud, Megilla 14a ,Yiscah was Sarah. She was called Yiscah (to see) because she saw the future through Divine inspiration (she was one of the seven prophetesses). She was also beautiful and all would gaze at her. Alternately, Yiscah is from the root meaning princely (nesichut), just as Sarah is from the root meaning ruling (srara).
Avraham later explains to Avimelech that Sarah is a member of his family (Breisheet 20:12) “In any case, she is my sister, the daughter of my father, but not the daughter of my mother and she became my wife.”
Rashi points out that Sarah was actually Avraham’s brother Haran’s daughter, making her Terach’s granddaughter and Avraham’s niece. However, one’s children’s children are like one’s own children. Family members referred to each other as brothers and sisters, as Avraham told Lot (Sarah’s brother) “we are bothers” even though Avraham was Lot’s uncle.
Breisheet Raba 44:10 points out that while she is named Sarai, she will not have children as she is barren. However, once her name is changed to Sarah, she is able to have a child as it says in Breisheet 21:1-2 “And God remembered Sarah as He had said and God did for Sarah as He had spoken. She conceived and gave birth to Avraham’s son in his old age at the designated time that God had declared.”
According to Rabbi Shimon ben Karcha, when her name was changed from Sarai to Sarah, the letter yud which has the value of ten was split into two letter heys which each have the value of five. One hey was given to Avram to become Avraham and one hey was given to Sarai to become Sarah, bestowing each one with a part of God’s name.
We see from the case of Sarah that a person’s name(s) can reflect who they are.