This article provides an analysis of the word "contrafactum" in the poetical texts of Thirteenth and Fourteenth centuries. First of all and prior to any Twentieth-century revision, the term had specific meaning referred to falsification, to appearance, to identity or emotion counterfeiting. Starting from Gennrich’s works, however, "contrafactum" starts to be referred to the practice of reusing previous melody for a new lyrical text (excluding the only Pfullinger Liederhandschrift, ms. Stuttgart, Landesbibliothek, Theol. 4° 190), changing the original sense of the term. This article proposes a concise review of the literary texts in which we can find the term in its original meaning. The aim of this research is to understand the context, the texts and textual traditions in which we have the word "contrafactum" between the thirtheenth and the fourteenth centuries, in relation to Italian and French poetical tradition, to medieval Latin poetical treaties (for example Dante’s De vulgari eloquentia), and to the technical lexicon of poetry and music in the Occitan vidas.