“Everyone” knows that Languedoc is named for the fact that the word for yes is oc, instead of oui. Everyone except a good friend of mine who claims that that is nonesense even though it has been widely believed for at least 800 years by all the authorities. That being the case, there is no point in citing authorities to prove him wrong. I guess if we could find something 1000 years that said something like, the people of the Midi speak a strange tongue in which they say oc for oui and some call it Languedoc. My friend has no alternative source for the name but just thinks this is a folk etymology. Can anyone refute him? Remember, no simple citing of authority, I want evidence.

Well, this site, which seems to be a rather official looking site on the region, has this to say:

Rough translation: This name “Occitania” […] was clearly a reference to “la langue d’OC” - “oc” meaning “yes”, spoken in that area.