There are at least three people named Tamar in the Bible:
• Tamar #1 was the widow of Judah's oldest son. According to custom, she was supposed to marry Judah's second son, Onan. If a child was born, that child would be the offspring of her first husband. But Onan did not carry out his duties according to the law, and because of this, he was struck dead by God. Judah's third son, Shelah, was next in line to marry Tamar, but Judah withheld Shelah from the marriage, fearing that he too would die. Tamar then disguised herself as a harlot, and was hired by Judah - who did not reconize the harlot as his former daughter-in-law. Tamar demanded Judah's staff and seal as a pledge of payment for her services. When she became pregnant, Tamar brought forth Judah's staff and seal, proving Judah was the father. She bore twin sons, Perez and Zerah. Perez was an ancestor of Jesus. (Genesis 38:6-30).
• Tamar #2 was a daughter of King David by Maacah, and the sister of Absalom (2 Samuel 13:1-22). She was raped by her half brother, Amnon, who pretended to be sick, and had Tamar bring food to him in his bedroom. To erase her shame, Tamar urged Amnon to marry her (there was no law against marriage between siblings at that time). But Amnon developed a hatred for Tamar, and the hatred "was greater than the love with which he had loved her" (2 Samuel 13:15), and he rebuked her. Tamar took her problem to her full brother, Absalom, who waited until the time was right, then arranged Amnon's murder at a party.
• Tamar #3 was the daughter of Absalom. "Absalom had three sons born to him, besides a daughter named Tamar, who was a beautiful woman" (2 Samuel 14:27). Obviously, Absalom named his daughter after his sister.
Tamar means "date palm."