Hadassah means "myrtle" and is the original Hebrew name of Esther. See Esther 2:7.
Here is a note about the Myrtle tree from Nelson's New Illustrated Bible Dictionary:
Myrtle. An evergreen tree with dark glossy leaves and white flowers. The leaves, flowers, and berries of the myrtle were used for perfume and as seasoning for food. The myrtle tree had a religious significance for the Jews (Zec_1:8-11) and was a symbol of peace and joy. Queen Esther's Hebrew name, Hadassah (Est_2:7), meant “myrtle.”
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