To clarify: not MD5 itself. It was created in 1991 by Ron Rivest. (It is my experience that knowledge of these things isn't as widely distributed as one might hope.)

I first came across it in 1995/1996: Wow, what a magical tool for backend web stuff! I used it for everything.

Wait, is that the same guy who co-authorer the Floyd-Rivest Algorithm? Hmm, looks like it[0]. Huh, neat.

[0] https://en.wikipedia.org/wiki/Floyd%E2%80%93Rivest_algorithm