Mizraim is the Hebrew word that is commonly translated as "Egypt," thus the Philistines are ethnically related to the Egyptians.
However, note that the Casluhim are divided into the Philistines and Caphtorim (in fact, the Philistines are frequently identified with Caphtor, the Hebrew name for at least the island of Crete and perhaps for the whole Aegean region; see Amos 9:7; Jeremiah 47:4). This indicates that their origins lie in the area of Crete, western Asia Minor, and the Aegean Sea, and modern archeology bears this out. For instance, Philistine pottery resembles that of the Minoan and Mycenaean (Homeric Greek) civilizations to the point that a material connection is beyond question. Other substantial links to the area include early Greek weapons, armor, dress, burial methods, military tactics, government, religion, etc.
How did these Aegean people end up settling in southwestern Canaan? The story is a long one, beginning in the days of Abraham. Being a restless, warlike, trading people, the Philistines frequently attempted to expand their influence, first through setting up trading colonies in distant lands and then by force of arms, if necessary. Genesis 21:34 records, "Abraham sojourned in the land of the Philistines many days," referring to the area around the town of Gerar, where Abimelech was king (see Genesis 20). This means that by the early nineteenth century bc, at least a small colony of Philistines had already gained a foothold in the land of Canaan.
Richard T. Ritenbaugh
Who Were the Philistines?