In the French colonies, some indigenous people wanted to give their children French names, but they didn't know them. So they looked the names of the saints in the calendar. However for the 14th of July French calendars generally don't show the name of this day's saint, but the fact that it's France's National Day, the “Fête nationale” in French, often abbreviated to “Fêt. Nat.”. This is how the first name “Fetnat” appeared.