Agagite

The term Agagite (אגגי) is used in the Book of Esther as a description of Haman. The term is understood to be an ethnonym although nothing is known with certainty about the people designated by the name.

According to Cheyne and Black, this term is used to label Haman, figuratively, as a "descendant" of Agag, the enemy of Israel and king of the Amalekites. "Haman, as an Amalekite, is opposed to Mordecai, the descendant of Kish (Esth[er] 2:5) ... The meaning is that there is an internecine struggle between the Jews and their enemies, like that between Saul and Agag of old." With this understanding, the Greek translator rendered the term "Macedonian."

A well known Midrashic explanation of the term relates it to King Agag of the Amalekites whereby it is viewed as meaning either a literal descendant of Agag or a symbolic term for an antisemite, due to the Amalekites being a perennial enemy to the Israelites.

Reliable sources include this one:  (from the "Chabad dot org" website) -- which is itself replete with footnotes. See e.g. the superscript numbers 10 through 13 in the "quote" field above -- [which are "expanded on" somewhat, here below]. It says that (or ... it explains "the sense in which") Agagites can be seen as both genetically [literally] and figuratively "descendants" of Amalek. Among the footnotes in that "chabad dot org" web page -- from which a portion of it is "d" above -- one can find these four "footnote" references to (biblical or 'commentary') sources: and
 * [10] "Samuel 15:3."
 * [11] "Rashi, [on] 25:19."
 * [12] "Samuel 15."
 * [13] "Esther Rabbah, Petichta 7." (Even if this source is not found on the "chabad dot org" web site, -- as "[10]" and "[12]" were -- it can be "looked up" at e.g. https://www.sefaria.org/Esther_Rabbah%2C_Petichta.7?lang=bi instead.) Note that the source referenced here ('Esther Rabbah') is considered to be a Midrashic source.