History of the modern term
Main cities of Occitania, written in the Occitan language
The name Occitan comes from lenga d'òc ("language of òc"), òc being the Occitan word for yes. While the term would have been in use orally for some time after the decline of Latin, as far as historical records show, the Italian medieval poet Dante was the first to have recorded the term lingua d'oc in writing. In his De vulgari eloquentia, he wrote in Latin, "nam alii oc, alii si, alii vero dicunt oil" ("for some say òc, others sì, yet others say oïl"), thereby highlighting three major Romance literary languages that were well known in Italy, based on each language's word for "yes", the òc language (Occitan), the oïl language (French), and the sì language (Sicilian and Italian). This was not, of course, the only defining characteristic of each group.
The word òc came from Vulgar Latin hoc ("this"), while oïl originated from Latin hoc illud ("this [is] it"). Old Catalan, and now the Catalan of Northern Catalonia also have hoc (òc). Other Romance languages derive their word for "yes" from the Latin sic, "thus [it is], [it was done], etc.", such as Spanish sí, Eastern Lombard sé, Sicilian and Italian sì, or Portuguese sim. In Modern Catalan, as in modern Spanish, sí is usually used as a response, although the language retains the word oi, akin to òc, which is sometimes used at the end of yes–no questions, and also in higher register as a positive response. French uses si to answer "yes" in response to questions that are asked in the negative sense: e.g., "Vous n'avez pas de frères?" "Si, j'en ai sept." ("You have no brothers?" "Yes [I do], I have seven.").
The name "Occitan" was attested around 1300 as occitanus, a crossing of oc and aquitanus (Aquitanian).
Other names for Occitan
For many centuries, the Occitan dialects (together with Catalan) were referred to as Limousin or Provençal, after the names of two regions lying within the modern Occitan-speaking area. After Frédéric Mistral's Félibrige movement in the 19th century, Provençal achieved the greatest literary recognition and so became the most popular term for Occitan.
According to Joseph Anglade, a philologist and specialist of medieval literature who helped impose the then archaic term Occitan as the sole correct name, the word Lemosin was first used to designate the language at the beginning of the 13th century by Catalan troubadour Raimon Vidal de Besalú(n) in his Razós de trobar:
La parladura Francesca val mais et [es] plus avinenz a far romanz e pasturellas; mas cella de Lemozin val mais per far vers et cansons et serventés; et per totas las terras de nostre lengage son de major autoritat li cantar de la lenga Lemosina que de negun'autra parladura, per qu'ieu vos en parlarai primeramen.
The French language is worthier and better suited for romances and pastourelles; but that (language) from Limousin is of greater value for writing poems and cançons and sirventés; and across the whole of the lands where our tongue is spoken, the literature in the Limousin language has more authority than any other dialect, wherefore I shall use this name in priority.
As for the word Provençal, it should not be taken as strictly meaning the language of Provence, but of Occitania as a whole, for "in the eleventh, the twelfth, and sometimes also the thirteenth centuries, one would understand under the name of Provence the whole territory of the old Provincia Romana and even Aquitaine". The term first came into fashion in Italy.
Currently, linguists use the terms "Provençal" and "Limousin" strictly to refer to specific varieties within Occitania, keeping the name "Occitan" for the language as a whole. Many non-specialists, however, continue to refer to the language as Provençal, causing some confusion.