The origins of the name Plateau

I don’t know whether Daphnée Hacker-B. reads my blog, but she writes about the origin of the neighbourhood name Plateau in Metro on Tuesday – although in a way that begs the question. Apparently it comes from the school called Le Plateau, on Calixa-Lavallée just inside Lafontaine Park. I can’t see anything from the school history section why it was given this name, if the neighbourhood wasn’t called the Plateau already.