One theory , is that they were descendants of Byzantine Empire's retired soldier who once they reached a certain (older)age, they were given land and kept as reserve troops known as apomaxoi
The official language of Byzantine empire was Latin until the 6th-7th century, and was certainly the lingua franca of the roman army. That the Vlach language has great similarities with Romanian it is only natural due to the the common roots of the languages, from eastern vulgar Latin. In the same manner that the iberian languages,the occitanian languages, the italian dialects have common orings in the vulgar latin accent spoken respectively in each region. Similarly, Romanian and Vlach descend from vulgar balkanic latin.
Another theory is that Vulgar latin came with refugees from Balkan interior pressured by the slavic or goth population migrations. Illyric tribes should have been thoroughly latinized(in the upper Balkans) as they have been in the Latin linguistic sphere of influence.
Either way Vlach and Romanian [FONT=q_serif, Georgia, Times, Times New Roman, Hiragino Kaku Gothic Pro, Meiryo, serif] intelligibility should be much lower than the one Spanish have with Portuguese. [/FONT]
