Easton's Bible Dictionary (1897)
A name applied to Haman and also to his father (Esther 3:1, 10; 8:3, 5). Probably it was equivalent to Amalekite.
Smith's Bible Dictionary (1863)
[Agag]
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
A'GAGITE. Haman is called an Agagite, perhaps because of his ancestry. Esth 3:1.