"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."
word-forming element used in forming nouns from Latin words ending in -atus, -atum (such as estate, primate, senate). Those that came to English via French often arrived with -at, but an -e was added after c. 1400 to indicate the long vowel. The suffix also can mark adjectives formed from Latin past participles in -atus, -ata (such as desolate, moderate, separate); again, they often were adopted in Middle English as -at, with an -e appended after c. 1400.
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Definitions of palatinate from WordNet
a territory under the jurisdiction of a count palatine;
a territory in southwestern Germany formerly ruled by the counts palatine;