This is perhaps only a general title of royalty applicable to the Philistine kings.
The name of two biblical kings:
The king with whom David sought refuge when he fled from Saul (1 Samuel 21:10-15). He is called Abimelech in the superscription of Psalms 34.
It was probably this same king to whom David traveled a second time at the head of a band of 600 warriors, and who assigned him Ziklag, with whom he carried on war against the surrounding tribes (1 Samuel 27:5-12).
Achish had great confidence in the valor and fidelity of David (1 Samuel 28:1-2), but at the instigation of his courtiers did not permit him to go up to battle along with the Philistine hosts (1 Samuel 29:2-11). David remained with Achish a year and four months.
Another king of Gath, probably grandson of the above king, to whom the two servants of Shimei fled. This led Shimei to go to Gath in pursuit of them, and the consequence was that Solomon put him to death (1 Kings 2:39-46).