Everyone from the PLO to a Mitt Romney spokesman jumped on Gingrich for this assertion, but he happens to be absolutely correct: no Arabic-speaking Muslims identified themselves as "Palestinian" until 1920, when, in rapid order this appellation and identity was adopted by the Muslim Arabs living in the British mandate of Palestine."
Daniel Pipes
For details, see a long article of Daniel Pipe's from 1989 on the topic or a short one from 2000. (December 10, 2011)