Flapper. The term originated in the early 1920s and referred to young, emancipated women breaking from the mold of convention with knee-high skirts, “bobbed” hair and rolled stockings.
As part of this defiance of social convention they wore their over shoes unbuckled so that the buckles flapped loudly in walking. So was born the name “flapper.”
(Information provided by “The Complete Footwear Dictionary: Second Edition” by Dr. William A. Rossi, 2000.)