“And he brought up Hadassah, that is, Esther, his uncle's daughter: for she had neither father nor mother, and the maid was fair and beautiful; whom Mordecai, when her father and mother were dead, took for his own daughter.”
King James Version (KJV)
2:7 Esther - Hadassah was her Hebrew name before her marriage; and she was called Esther by the king after it.