I originally bought the domain tldraw.com for a different project, Telestrator (https://github.com/steveruizok/telestrator), which is an app for drawing on top of your screen during a call / stream. The app is pretty nice if you're on macOS, but I never used the domain.

When this project kicked off, I wanted something that could be saved alongside code as version-controlled documentation, and that was the first time I noticed the "tldr" in "tldraw". So I just used tldraw.com and stole the name!