1911 Encyclopædia Britannica/Patois

PATOIS, a French term strictly confined to the dialect of a district or locality in a country which has a common literary language, often used of the form of a common language as spoken by illiterate or uneducated persons, marked by vulgarisms in pronunciation, grammar, &c. The origin of the word is not certain. It has been taken to be a corruption of patrois, from Low Lat. partriensis, of or belonging to one’s patria, or native country, fatherland.