French "dit/dite" Names
Researching French ancestry with "dit/dite" names is mind-boggling until you get used to it. They're called "dit" names for males or "dites" for females. Literally, France couldn't figure out how they wanted to handle the new invention of the surname until Napoleon just put an end to it in the 1800s. They routinely interchanged two different names and would hyphenate them only for the Church.
You could have a man named Hugues Picard who also used the name Hugues LaFortune. When he signed a contract, he could use either name. But when he went before God, he was Hugues Picard-dit-LaFortune. BUT...his children might be baptized under either name and later use the other. That was up to the priest to keep straight. The LaFortune might develop because he inherited a large fortune that he wasn't expecting, or got into a business venture that reaped unexpected windfalls.
Now here's the funny part about "dit/dite" names.... The sons of this man might take either name with them as their own surname, then develop their own dit names. So Hugues might have fathered Pierre and Rene. Pierre Picard could take the dit name LaGuerre because he was a great soldier. His brother might become Rene LaFortune and take the dit name LaVigne because he was a great vintner. A few generations of this and you'll be begging for the good old days of Dutch patrynomics.
It takes a while to figure it out, but once you do, just muddle through until you get to some semblance of stability. The 1600s and 1700s are the worst. The 1400s and 1500s are far better.
Also know that in France, surnames weren't required until the 1600s. So you can have some regions still using patrynoms or they would use their patron saint for their surname. You might find someone name Martin-Jacques Gilles-St-Martin. His name was Martin, son of Gilles, whose patron was St-Martin. That's usually in the Franche-Comte and other eastern provinces where education was lacking. The parish priest kept all the records, and they didn't have much contact with the outside world, so they didn't worry about this "surname" craziness.