Last night I was at our family history center, and I found the book with the explanation of the word "dit".This is what it says....
Briefly: it was the custom in some French families for one or more of the sons to adopt a distinguishing nickname, added to the surname and preceded by "dit" (which may be roughly translated as "who is called").These dit names sometimes were used more frequently than the actual family name and as years passed, the old family name disappeared and the "dit" name replaced it.
An excellent example is found in three sons of Gilles Chavin of Montreal, who settled in the Illinois country about 1735.Louis Chavin only used the family name.His brother Joseph was Chavin dit Charleville; their brother Philippe was Chavin dit Joyeuse.Joseph signed his name Charleville and his decendants are known by that name today.Philippe died young but his son Francois was Chauvin dit Joyeuse in his marriage record and his present-day descendants are called Joyce.Yet they are all Chauvins and the researcher tracing them would need to be aware of the "dit" usage.
Is this "dit" name a clue to other information about the family?Very seldom.A man might choose his "dit" because he liked the sound of it, because he knew and liked someone with that name, because it was the name of the old family home, or for some other unknown reason.In the case of Philippe Chauvin dit Joyeuse, we do not know whether he was called joyous because he was, or--sardonically--because he was not.Nor do we know why some brothers took a "dit" name and others didn't, or why the custom prvailed in some families and not in others.
On occasions the "dit" name appears without the "dit"--Chauvin Chareville is as example--and it might appear to be a middle name.But if you find such an example among the names you're researching, it is quite possibe that one is a "dit" name and should be viewed as a surname in furthur research.