"It is well known that French is in the main a descendant from
the Latin, not the Latin of Rome, but the corrupter Latin
which was spoken in Gaul. Now these Latin-speaking Gauls did
not, for some reason, say 'est,' 'it is,' for 'yes,' as the
Romans did; but they used a pronoun, either 'ille,' 'he,' or
'hoc,' 'this.' When, therefore, a Gaul desired to say 'yes,'
he nodded, and said 'he' or else 'this,' meaning 'He is so,'
or 'This is so.' As it happens the Gauls of the north said
'ille,' and those of the south said 'hoc,' and these words
gradually got corrupted into two meaningless words, 'oui' and
'oc.' It is well known that the people in the south of France
were especially distinguished by using the word 'oc' instead
of 'oui' for 'yes,' so that their 'dialect' got to be called
the 'langue d'oc,' and this word Langue-doc gave the name to a
province of France."
_C. F. Keary,
Dawn of History,
chapter 3._
ALSO IN:
_F. Hueffer,
The Troubadours,
chapter 1._
_Sir G. C. Lewis,
The Romance Languages,
page 52, and after._