royalty (n.)

mid-13c., "fit for a king;" late 14c., "pertaining to a king," from Old French roial "royal, regal; splendid, magnificent" (12c., Modern French royal), from Latin regalis "of a king, kingly, royal, regal," from rex (genitive regis) "king," from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule."

Of institutions, "founded under the patronage of a sovereign" (c. 1500). The meaning "splendid, first-rate" is by 1853. The U.S. colloquial use as an emphasizer, "thorough, total" is attested from 1940s. Battle royal (1670s) preserves the French pattern of adjective after noun (as in attorney general); the sense of the adjective here is "on a grand scale" (compare pair-royal "three of a kind in cards or dice," c. 1600). Royal Oak was the name given to the tree in Boscobel in Shropshire after Charles II hid himself in it during flight from the Battle of Worcester in 1651. Sprigs of oak were worn to commemorate his restoration in 1660.

1660s, "real estate, real property," from earlier meaning "a real possession" (1540s), earlier still "reality" (mid-15c.), from Old French realite, realte, from Medieval Latin realitatem (nominative realitas), from Late Latin realis "actual" (see real (adj.)). The notion behind the word is the immobility, or the fixed, permanent nature of certain kinds of property, especially landed. Also compare reality.

early 15c., casuelte, caswelte, "chance, accident; incidental charge," from casual (adj.) on the model of royalty, penalty, etc. From the earliest use especially of untoward events or misfortunes. The meaning "losses in numbers from a military or other troop" is from late 15c. The meaning "an individual killed, wounded, or lost in battle" is from 1844. Casuality had some currency 16c.-17c. in the sense "chance, a chance occurrence," especially an unfortunate one, but now is obsolete.