When I worked in a nursing home in the '70s, we had a male resident of French Canadian descent whose first name was Hyacinthe. (No, his last name was not Bucket or Bouquet.) His nickname was Hetty, which I've always thought of as a nickname for Henrietta. If I were a male Hyacinthe, I'd probably go by Hy.
Another French Canadian resident had a sister named Fernande, who went by Fern. Fernande was actually her middle name. All the girls in this large family had the first name Marie, and all the boys had the first name Joseph -- they went by their middle names.
I have only a nodding acquaintance with French, but it seems to be a fairly common French thing to feminize a male name by adding an E, or double the final consonant and then add an E (Jean --> Jeanne, Michel --> Michelle). Which isn't much different from what English speakers do when we feminize a male name by adding an A (Paula, Erica, Michaela). But it doesn't explain a man named Hyacinthe.