Agag had been the title of the king of the Amalekites since the time of the Exodus. He and his people were a perennial enemy of the people of God. The prophet and judge Samuel gave Saul a command from the LORD to destroy the Amalekites left in the land. The new king of Israel spared the last king that people as a trophy.
Samuel, upon arrival to the camp, completed the task God had demanded of the king. He ordered Agag to be brought out and personally cut him into pieces
The word agag (אֲגָג) is of uncertain origin, but seems to be related to the word agé (אָגֵא). The words seem to reflect the flickering brightness of a flame atop a candle or lamp. One can imagine that one would bear it with pride as a name or a title.
The tribe of Amalek, a descendant of Esau (Edom), had become a fierce and territorial foe. They had stood against the wandering tribes of Israel in their exodus from Egypt. When defeated by the forces of Joshua under Moses, they retreated and resurfaced in the days of the judges in an alliance with the Canaanites in the land.
As the tribe fiercely defended its territory, it followed the custom of others around them, conferring the title of Agag to the leader of the ruling class. The leader that faced Saul's forces did not have the allies that his forefathers had, but God's curse on the enemy of His people became the first order of business for the first king of the united tribes of Israel.
Death and Legacy
The tribe of the Amalekites had apparently been splintered in skirmishes among under Deborah and Barak, for the death of this Agag along with his people did not eliminate the threat. In the days of Saul's successor, David, the threat receded into the wilderness, only to resurface as "Agagites", Edomites that were taken into captivity at the fall of Judah.
In the dark days of the captivity, under the Persian King Ahasuerus and his new queen Esther, a man named Haman rose to a prominent place in the cabinet. He was an Agagite, a band of Edomites loyal to the conquerors. Tribal memory went back beyond the Davidic dynasty to the first king, a Benjamite. The hatred remained against all the Jews for centuries.