Anyone doing French-Canadian family research will, at one point or another, discover one or more of their ancestors had a dit name, such as Dargie dit Desrosiers. Before we even start to discuss these so called dit names, we should make clear what they are not: definitely not a nickname, positively not an alias and assuredly not an a.k.a. (also know as), although in time, that is what it came to mean. The word dit mean 'said' in French.
A dit name, in fact, was an extension to an existing name, and became part and parcel of the original basic name. The custom of having dit names first began amongst the nobles and kings. It was a matter of positive identity. As an example: Guillaume, Duke of Normandie--because of his many military conquests--had the name "Guillaume dit le Conquerant." Then, in 1066, when he invaded and conquered England, the English people had difficulty in pronouncing his French name of Guillaume and they called him "Gillium," but that quickly became "William." His French dit name of Guillaume dit le Conquerant then became "William the Conqueror."
The use of dit names did not come into common usage until the late 1500's, when they became popular in France. As the population grew and the same names given to too many of a family, it became necessary to sort them out.
Thus, an additional designation might describe a person (Le Gros) or tell where he lived (La Rivière)--it might identify his occupation (Boulanger) or a quality of his personality (La Bonté).
The custom was extended to the military. In the early 1600's, any young man entering the service was assigned a dit name, usually taken from an attribute of the man.
All of this was brought to New France. Now, three and four hundred years later, we are still trying to figure some of them out.
This article, in part, was written by Frank R. Binette of New Hampshire, who wrote it for Lifelines in 1994.