The Anglicized word "Philistine" means "a native or inhabitant of ancient Philistia," and comes from the Hebrew word פלישתי (p’liysh’tiy, Strong’s #6430). To define this word we need to examine the root of this word.
The root word פלש (P.L.Sh, Strong’s #6428) is a verb meaning "to wallow" or "to roll." Derived from this verb is the noun לשת (peleshet, Strong’s #6429). This noun is not used in the Biblical text, except as the name of a place (Philistia), and its meaning is uncertain, but probably means a "wallower" (one who wallows) or something to that effect.
The word פלישתי (p’liysh’tiy, Strong’s #6430) literally means "one of peleshet/Philistia." The plural form is פלישתים (peliyshtim) and literally means "ones of peleshet/Philistia."