Vaudeville
2 of the 7 encyclopedias on this shelf carry an entry for Vaudeville. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a term originally applied to a country song of like kind with those written by Oliver Basselin, of the valleys of Vaux de Vire, in Normandy, in the 15th century. These songs, which were satirical, had for their subjects love, drinking, and passing events. They became very popular and were spread all over France under the name Lais des Vaux de Vire. The peculiarity of their character lived after their origin was forgotten, and plays, interspersed with songs of this description, came to be called Vaudevilles, and occasionally Virelais. Also a light gay song, frequently embodying a satire, consisting of several couplets and refrain burden, sung to a familiar air, and often introduced into theatrical pieces; a ballad, a topical song. In French drama a piece whose dialogue is intermingled with light or comic songs sung to popular airs. In the United States of late years the term has come into use to denote light or "variety" theatrical entertainments, especially when continuous.
Aiton's Encyclopedia (1910)
vod'vil, originally a country ballad or song. The term is French, referring to the "vau," or valley of the river Vire in Normandy. Many popular country songs originated here about the close of the fourteenth century. They became known as vaudeville. Writers of comedy learned to use these light, gay songs to break up a play. In this way comic opera, in which singing and dancing form a prominent part, has come to be known as vaudeville. The term is applied with perfect propriety to any light, entertaining comedy, and has no necessary connection whatever with evil associations. See Comedy