Interesting. Like I said in another comment in Italian it means exactly what I said. From the first line on the topic on Italian wikipedia:

A vasistas (also written wasistas) is a type of window that is also opeaneable on the inside [...]. The system allows the door to rotate down and the opening is delimited by special stops, called opening delimiters.

But apparently, after reading the French wikipedia page they use that word for something else. So it appears that we did steal the word from them, but used it to describe something different.