Albert Barnes Commentary Esther 2:10

"Esther had not made known her people nor her kindred; for Mordecai had charged her that she should not make it known." — Esther 2:10 (ASV)

The Persians had no special contempt for the Jews; but, of course, they despised more or less all the subject races. Esther, with her name that was characteristic of the Persian people, may have passed for a native Persian.