As a former MS employee some time ago I don't think I ever heard "windev". It was always referred to as "Windows". Though there were a lot of different groups within that, so sometimes you'd hear an initialism for a specific team. For example during some of my time there was a big organizational split between "core" and more UI oriented teams.

For a moment there I thought you were referring to this trademark: https://pcsoft.fr/windev/index.html Which was known at a time for having young women in light clothing in their marketing material.