"possessing quasi-royal privileges," literally "pertaining to a palace," mid-15c., of counties, "ruled by a lord who has privileges resembling those of an independent sovereign," from Old French palatin (15c.) and directly from Medieval Latin palatinus "of the palace" (of the Caesars), from Latin palatium (see palace). Medieval Latin (comes) palatinus was a title given to one holding any office in the palace of a prince, hence "possessing royal privileges." A doublet of paladin.
In reference to the Rhineland state, formerly an electorate in the old German empire, by 1570s; by 1709 as a noun meaning "resident of or immigrant from the (German) Palatine."