The French had naming traditions that started with family and involved Church.
Every first-born son was generally named after the paternal grandfather. The second-born son was named after the maternal grandfather.
The first two daughters were generally named after their grandmothers. The order would flip-flop, depending on whether one was dead or not. Since maternal mortality was high, you'll often see the name of a deceased grandmother being used over and over again.
The next thing you'll run into is that most newborn babies were given a hyphenated name. Victor-Marie and Marie-Genevieve are two examples. The first is a male name who would be called Victor, with his female patron saint being honored in his name. But if it were used for a female, it would be that her name was Marie (and that would be the name in civil records). But St-Victor was her patron saint and it was the name under which all of her church records would be found.
The second is the more common pre-1780...no flip-flopping of name usage. In that one, her patron saint was Ste-Marie and her given name was Genevieve. You'll find her always being called Marie-Genevieve in official records, except for censuses. There, only the common name "Genevieve" was used.
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