I cannot stress this enough that the French word for fox, renard, is the name of a fictional fox from medieval stories.
The fox in French was originally called goupil, derived from the Latin vulpiculus, (small vulpes).
But the medieval Roman de Renart (Reynard the Fox) and other writings gave the title character the name of Renart, equivalent to the German Reinhart or Reinhard. And it was so popular that the name became a byword for the fox (he’s cunning as Renart) and eventually supplanted goupil as the animal’s name.
This is wild. It’s as if “seagull” was dropped from English and replaced by jonathans. Or something.
Actually that did happen! (sort of) A lot of the names of British garden birds come from the craze of giving birds Christian names - Jenny wren, Robin redbreast and so on. In some cases this resulted in the bird’s original name being dropped and the name being kept to mean the bird, as in the case with the robin.
Can’t find any comprehensive sources on the phenomenon but this blog mentions it:
As does the wikipedia article for robin:
