The French idiom “montrer patte blanche” translates literally as “to show white paw.” What it really means is “to prove your identity,” “to present authorisation to enter a place,” or “to be recommendable.”

This saying dates back to the time of Jean de La Fontaine. He was a poet and a writer of fables who lived in the mid 17th century.

One of his fables was called “The wolf, the goat and the baby goat.” The baby goat, known as a kid, was left at home, alone, by its mother. The kid’s mother had white paws. The mother told the kid not to open the door to anyone who didn’t have white paws.

While the mother was out, a wolf came to the door. The kid asked the wolf to show its white paws. Being unable to do this, the wolf was angry and frustrated. But the kid remained safe.

There is no equivalent expression in English.