An Explanation of "Dit" Names
One thing that can make it difficult to find an ancestor is that he/she may have been using a different surname from the one that you expect. It is necessary to become aware of any "dit" names that might be associated with the surname you're tracing, and if you can't find someone under the name of his child, you may find him under the dit name.
"Dit" in French means "say" and in this context, it means "called." In other words, a person might be Pierre Bourbeau dit Lacourse, which means that he had an ancestor named Bourbeau, but he chooses to use the name Lacourse instead. So he is Pierre Bourbeau called Lacourse.
People might take a dit name to distinguish their family from another family of the same name living nearby. Often it was a sort of nickname, often picked up during service as a soldier. Or it might refer to the place in France where the family originated. Sometimes it was the mother's surname, and sometimes the father's first name was used, either instead of the surname (for example, Hebert dit Emmanuel) or in addition to it (Jeanbard, Castonquay). In any case, very often the dit name was passed down to later generations, either in place of the original surname, or in addition to it.
Name Variations of “Dit” Names
Some children might then keep the original surname (e.g. Barbeau), and some might use the dit name (e.g. Lacourse). After a few generations, it's not uncommon to completely lose the memory of the original name, or to forget which was the original and which was the dit name. The best example of this is the Hudon dit Beaulieu family, where you will often find people listed as Beaulieu dit Hudon. You sometimes might find a name and its dit name hyphenated, as in François Hudon-Beaulieu. In fact, you can generally assume that a hyphenated surname (before 1950, anyway) is the surname plus dit name. Just remember that any Hudon might be the child of a Beaulieu and vice versa.
Some surnames, such as Roy, have had several different dit names. You should be aware that usually a different dit name indicates a different family. For example, Siméon Roy dit Audy and Antoine Roy dit Desjardins were not related to each other. So it helps us to distinguish who's who among their descendants if the descendants use a dit name. Pierre Roy dit Audy will be a descendant of Siméon, and François Roy dit Desjardins will be a descendant of Antoine.
The sources you use may give the name as it appeared in the original document, or may list all the Hudons and Beaulieus together, under either name. Jette has standardized spellings, and leaves out "de" when alphabetizing, but he is faithful to the original surname of the family. So whether you're looking for a Hudon, a Beaulieu, or a Hudon-Beaulieu, they're all listed together under "H." Other sources may list the same person many different places, and some sources consider Beaulieu to be more common, and therefore they place the Hudons under "B." Don't assume a marriage or birth isn't listed until you've exhausted all possible names and spellings.
The can also be many spelling variations to a name. Any name that starts with a vowel, for example, might also be found with an H in front of it (Emond, Hemond, Ayot, Hayot). And the "o" sound at the end of a name might be spelled ot, eau, au, ault, eault, eau, aux, eaux, aud, or aut.
Some examples of variations of the Blouin name are:
Bellouin, Beslouin, Beloin; and of course Blouin dit Laviolette