There's a long history of Unix-like environments on Windows dating to the 1980s: MKS Toolkit (Mortice Kern Systems, later incorporated into Windows Services for Unix, precursor of WSL), UWIN from David Korn, Cygwin, and others.

I'd experimented with several of these before I realised that what I wanted wasn't Windows running Unix-like utilities, but a real honest-to-goddess Unix system, which was spelled "Linux".