palatine adj.

early 13c., palais, "official residence of an emperor, king, queen, archbishop, etc.," from Old French palais "palace, court" and directly from Medieval Latin palacium "a palace" (source of Spanish palacio, Italian palazzo), from Latin palatium "the Palatine hill," in plural, "a palace," from Mons Palatinus "the Palatine Hill," one of the seven hills of ancient Rome, where Augustus Caesar's house stood (the original "palace"), later the site of the splendid residence built by Nero. In English, the general sense of "magnificent, stately, or splendid dwelling place" is by c. 1300.

The hill name perhaps is ultimately from palus "stake" (see pale (n.)) on the notion of "enclosure." Another guess is that it is from Etruscan and connected with Pales, the supposed name of an Italic goddess of shepherds and cattle. De Vaan connects it with palatum "roof of the mouth; dome, vault," and writes, "Since the 'palate' can be referred to as a 'flattened' or 'vaulted' part, and since hills are also often referred to as 'flat' or 'vaulted' (if their form so suggests), a derivation of Palatium from palatum is quite conceivable."

French palais is the source of German Palast, Swedish palats and some other Germanic forms. Others, such as Old English palant, Middle High German phalanze (modern German Pfalz) are from the Medieval Latin word. 

1590s, in reference to the medieval romance cycle, "one of the twelve knightly champions in attendance on Charlemagne and accompanying him to war," from French paladin "a warrior" (16c.), from Italian paladino, from Latin palatinus "palace official;" noun use of palatinus "of the palace" (see palace).

The Old French form of the word was palaisin (which gave Middle English palasin, c. 1400); the Italian form prevailed because, though the matter was French, most of the poets who wrote the romances were Italians. Extended sense of "a heroic champion" is by 1788.

"the office or province of a palatine ruler," 1650s, from palatine + -ate (1). In England and Ireland, a county palatine; also used of certain American colonies (Carolina, Maryland, Maine).