That is balderdash. “Semitic” is a term applied to a language group that includes Hebrew and Arabic. Jews originated in the area of modern Israel. “Palestinians” are from the area around modern Israel (Syria, mostly) and speak Arabic because they were conquered by Arabs (from Arabia) during the great Islamic Imperialist Wars, in the 7th Century.
“A DNA study of Jews and Palestinian Arabs (including Bedouins) found that these were more closely related to each other than to people of the Arabian Peninsula, Ethiopian Semitic-speaking people (Amharas, Tigrayans, Harari and Tigre people), and the Arabic speakers of North Africa.”
“Genetic studies indicate that modern Jews (Ashkenazi, Sephardic and Mizrahi specifically), Levantine Arabs, Assyrians, Samaritans, Maronites, Druze, Mandaeans, and Mhallami, all have an ancient indigenous common Near Eastern heritage which can be genetically mapped back to the ancient Fertile Crescent, but often also display genetic profiles distinct from one another, indicating the different histories of these peoples.”