They were called a Palestinians in Arabia in 1950. Herodotus called the Syrian province Palestine in 500 BC.You have mentioned that many times.
Shakespeare and Chaucer wrote about Palestine after the Romans changed Judea to Syria Palestine, incorporating Syria.
Calling a place Palestine, is not the same as calling any of the people living there Palestinian at the time.
One cannot find ONE history book, Greeks, Romans, Assyrians, Byzantine, or even the Kurd or Arab Muslims, refer to ANY people living on the land they invaded as Palestinians.
The Palestinian nationality was born in Moscow in 1963 when Arafat conjured it with the KGB, as another weapon to destroy Israel.
They are Palestinians since then, but never before that. Not even during the Mandate the Arabs cared to be called Palestinians, they wanted to be part of Greater Syria and be called Syrians.
Take a look at the Palestine Papers at the Avon Project Yale law school.