O.E. gliu "entertainment, mirth, jest," presumably from a P.Gmc. *gliujan but absent in other Gmc. languages except for the rare O.N. gly. In O.E., an entertainer was a gleuman. A poetic word in M.E., obsolete c.1500-c.1700, it somehow found its way back to currency late 18c. Glee club (1814) is from
the secondary O.E. sense of "unaccompanied part-song," as a form of musical entertainment.