When Did Arabs Come to 'Palestine'?

From this book, The nationalist crusade in Syria by Elizabeth P. MacCallum. New York : The Foreign Policy Association, 1928, full text here:

The Muslim conquest of Syria and Palestine in the seventh century CE.

And what was the imagined territory if this Syria?

Jerusalem was but a vilayet, a regional administrative unit, not part of a country called Palestine'.

And another source, referring to the year 1937 from this book:-

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