The metrical fables of the Trouvères, or early poets north of the Loire, in the twelfth and thirteenth centuries. The word fable, in this case, is used very widely, for it includes not only such tales as Reynard the Fox, but all sorts of familiar incidents of knavery and intrigue, all sorts of legends and family traditions. The fabliau of Aucassin and Nicolette is full of interesting incidents, and contains much true pathos and beautiful poetry.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Fabliaux from Fact Monster: