In both American and British English, the primary emphasis is on the first syllable. The difference mainly lies in the articulation of the second syllable, which is slightly more clipped in British English.
The name "Palestine" originates from the word "Philistia," the term used to describe the land of the Philistines, a people who settled in the coastal areas of the region around the 12th century BC. The name was later adopted by the Greeks, who called the area "Palaistinē." The Romans adopted this name in a broader sense to include the regions of Judea and Galilee after they crushed the Bar Kokhba revolt in 135 AD, renaming the area Syria Palaestina as a punitive measure. Over the centuries, the name has been used in various forms to refer to different parts of this region.