This bit of Emacs Lisp absolutely comes from a more innocent time on the Internet. Looking at it, it seems I wrote the first version, at least as a proper package, back in 2001. It's very possible that I carried a non-package version of it around as part of dp-lib.el1 for some time before, so it might date from the late 1990s. While we weren't absolutely innocent back then, the idea of a slightly-risky-looking URL wasn't quite so bad as it is now.
So obfusurl.el came about from my time on Usenet, where sometimes you'd want to post a URL that would otherwise be a spoiler. This package was my solution to that. It's a simple idea: keep the protocol and domain and so on visible, just hide the remaining part. So rather than post:
https://blog.davep.org/about/
You'd post:
https://blog.davep.org/%61%62%6f%75%74/
I suppose this is still useful today, although I would expect a lot of people to be way less likely to want to attempt that click -- readable domain or not.
But, anyway, the code needed a tidy and cleanup for today's Emacs and Emacs Lisp. So obfusurl.el v2.2 now exists.
For a good chunk of my first decade of using Emacs, I carried a lot of personal code around in a rather large "library" file. ↩