Prior to the PLO Charter being released in 1964, no one referred to "Palestinians" with the same intent as used today
Here is a quote from Zuheir Mohsen, a senior PLO leader, in 1977:
“The Palestinian people do not exist. The creation of a Palestinian state is only a means for continuing our struggle against the state of Israel for our Arab unity… Only for political and tactical reasons do we speak today about the existence of a Palestinian people, since Arab national interests demand that we posit the existence of a distinct ‘Palestinian people’ to oppose Zionism. Yes, the existence of a separate Palestinian identity exists only for tactical reasons.”
PHOTO and VIDEO: Use according to Section 27 A