In response to those who think of the biblical origins of Tamar as tragic, I must disagree. While the first Tamar was put in a bad situation by the men in her life, she took matters into her own hands and fixed it. I find it to be a story of a strong woman standing up for herself and her rights. As for the second Tamar, as someone already noted, she would have been a direct descendant of the first one, so it would have been normal for her to have been named after her. (Anyone else have a middle or first name after family?)
Tamar is one of several British rivers whose ancient name is assumed to be derived from a prehistoric river word apparently meaning "dark flowing" and which it shares with the River Thames.
― Anonymous User 1/3/2012
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"Tamar" is also the word for the fruit of the palm tree, in other words "date".