loyal: [16] Loyal, ultimately the same word as legal, has a double history in English. It was originally acquired in the 13th century as leal. This came from Anglo-Norman leal, a descendant of Latin lēgālis ‘legal’. Then in the 16th century it was reborrowed from the modern French form loyal. The semantic link is ‘faithfully carrying out (legal) obligations’. => legal
loyal (adj.)
1530s, in reference to subjects of sovereigns or governments, from Middle French loyal, from Old French loial, leal "of good quality; faithful; honorable; law-abiding; legitimate, born in wedlock," from Latin legalem, from lex "law." In most cases it has displaced Middle English leal, which is from the same French source. Sense development in English is feudal, via notion of "faithful in carrying out legal obligations." In a general sense (of dogs, lovers, etc.), from c. 1600. As a noun meaning "those who are loyal" from 1530s (originally often in plural).