From BiblePortal Wikipedia

Hastings' Dictionary of the Bible [1]

Agagite . The designation of Haman (  Esther 3:1;   Esther 3:10;   Esther 8:3;   Esther 8:5;   Esther 9:24 ). Josephus ( Ant. XI. vi. 5) calls him an Amalekite. The epithet in Esther indicates that, as Agag was Saul’s adversary, so Haman was the foe of this other Benjamite. The LXX [Note: Septuagint.] reads Bugaios ,   Esther 3:1 ,   Esther 8:5 , omits at   Esther 3:10 , and at   Esther 9:24 , EST 16:10 has Macedonian , a word of evil connotation after Antiochus Epiphanes.

J. Taylor.

Morrish Bible Dictionary [2]

Haman was the son of Hammedatha the Agagite.  Esther 3:1-10;  Esther 8:3,5;  Esther 9:24 . Fürst says the Gentile name "of Haman is therefore explained by Josephus τὸ γένος Ἀμαλεκίτες and so too by Jewish tradition." That is, that Haman was an Amalekite. This explains why Mordecai refused to bow down before Haman. He was of that race with which Jehovah had sworn to have war for ever, and which Saul was directed to utterly exterminate.  Exodus 17:16;  Deuteronomy 25:19;  1 Samuel 15:3 .

Easton's Bible Dictionary [3]

 Esther 3:1,10 8:3,5

Holman Bible Dictionary [4]

 Esther 3:1Agag

International Standard Bible Encyclopedia [5]

ā´gag - ı̄t , (אגגי , 'ăghāghı̄ , from, אגג , 'ăghagh , "a member of the house of Agag"): A title of opprobrium given to Haman ( Esther 3:1 ,  Esther 3:10;  Esther 8:3 ,  Esther 8:5;  Esther 9:24 ). Jewish tradition always assigned the arch-enemies of Israel membership in the house of Amalek, the hereditary foe of the nation. Compare Ant , XI, vi, 5. The word Agag has properly been taken by Delitzsch as related to the Assyrian agagu , "to be powerful," "vehement," "angry." In the Greek parts of Esther, Haman is termed a Macedonian ( Esther 3:1 ,  Esther 3:10 ). The name Haman is probably of Elamitic origin. Oppert's attempt to connect the term "Agagite" with "Agaz," a Median tribe mentioned by Sargon, has found no supporters. See Agag .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [6]

[others A gagite] (Heb. Agagi , אֲגָגי , Sept. Βουγαῖος , Μακέδων , Vulg. Aggites), the name of the nation to which Haman (q.v.) belonged ( Esther 3:1;  Esther 3:10;  Esther 8:3;  Esther 8:5;  Esther 9:24). Josephus explains it as meaning Amalekite (Ant. 11, 6, 5), (See Agag).

Kitto's Popular Cyclopedia of Biblial Literature [7]

Agagite, used as a Gentile name for Amalekite in  Esther 3:1;  Esther 3:10;  Esther 8:3;  Esther 8:5.