1500s, earlier haliday (c. 1200), from Old English haligdæg "holy day, consecrated day, religious anniversary; Sabbath," from halig "holy" (see holy) + dæg "day" (see day); in 14c. meaning both "religious festival" and "day of exemption from labor and recreation," but pronunciation and sense diverged 16c. As an adjective mid-15c. Happy holidays is from mid-19c., in British English, with reference to summer vacation from school. As a Christmastime greeting, by 1937, American English, in Camel cigarette ads.
"to pass the holidays," 1869, from holiday (n.).