It was illegal--it's still illegal in France to name a baby a name that is not officially approved, absolutely--or even to adopt one.

给婴儿取一个没有被官方认可的名字,是违法的,至今仍是如此,完全不被允许,领养也不行

耶鲁公开课 - 1871年后的法国课程节选

And there were cases where Bretons tried to name their children Breton names and the French State said, uh-uh,pas possible, because it wasn't officially French.

还有一些布里多尼人,想要给他们的孩子取布里多尼的名字,但是法国政府说,想都别想,这并非官方法语

耶鲁公开课 - 1871年后的法国课程节选