What is the X in X-mas?
Old English gliu, gliw "entertainment, mirth, jest, play, sport," presumably from a Proto-Germanic *gleujam but absent in other Germanic languages except for the rare Old Norse gly "joy;" probably related to glad. A poetry word in Old English and Middle English, obsolete c.1500-c.1700, it somehow found its way back to currency late 18c. In Old English, an entertainer was a gleuman (female gleo-mægden). Glee club (1814) is from the secondary sense of "unaccompanied part-song" (1650s) as a form of musical entertainment.
(from Old English gleo: "music" or "entertainment," used in this sense in Beowulf), vocal composition for three or more unaccompanied solo male voices, including a countertenor. It consists of several short sections of contrasting character or mood, each ending in a full close, or cadence, and its text is often concerned with eating and drinking. In style it is homophonic-i.e., based on chords rather than on interwoven melodies. Although the first composer to use the term for a musical work was John Playford (1652), the glee flourished from about 1740 to about 1830. By the late 18th century, glees were also composed for mixed voices (male and female). The term is also loosely applied to various vocal compositions of the 17th-19th centuries that do not conform to these characteristics-e.g., the instrumentally accompanied part-songs by Henry Bishop