Kitto's Popular Cyclopedia of Biblial Literature
A´gag, the name of two kings of the Amalekites, and perhaps a common name of all their kings, like Pharaoh in Egypt (comp. Numbers 24:7; 1 Samuel 15:8-9; 1 Samuel 15:20; 1 Samuel 15:32). The first of these passages would imply that the king of the Amalekites was, then at least, a greater monarch, and his people a greater people, than is commonly imagined [AMALEKITES]. The latter references are to that king of the Amalekites who was spared by Saul, contrary to that solemn vow of devotement to destruction, whereby the nation, as such, had of old precluded itself from giving any quarter to that people (Exodus 17:14; Deuteronomy 25:17-19). Hence, when Samuel arrived in the camp of Saul, he ordered Agag to be brought forth. He came 'pleasantly,' deeming secure the life which the king had spared. But the prophet ordered him to be cut in pieces; and the expression which he employed—'As thy sword hath made women childless, so shall thy mother be childless among women'—indicates that, apart from the obligations of the vow, some such example of retributive justice was intended as had been exercised in the case of Adonibezek; or, in other words, that Agag had made himself infamous by the same treatment of some prisoners of distinction (probably Israelites) as he now received from Samuel. The unusual mode in which his death was inflicted strongly supports this conclusion.
Kitto, John, ed. Entry for 'Agag'. "Kitto's Popular Cyclopedia of Biblial Literature". https://www.studylight.org/encyclopedias/eng/kbe/a/agag.html.