TinyMUD is the name of a MUD server codebase, and the first MUD running that codebase. The MUD itself has subsequently come to be known as "TinyMUD Classic" or simply "Classic", or occasionally "DaisyMUD" (since in the final days of its first incarnation, it ran on a computer named "daisy"). To distance itself from the combat oriented traditional MUDs it was said that the "D" in TinyMUD stood for Multi-User "Domain" or "Dimension", which led to the eventual adoption of the term MU* to refer to TinyMUD and its many derivatives.
Most modern MUSHes are descended from TinyMUD.
The TinyMUD server was originally written by James Aspnes in mid-to-late 1989 with the intention of focusing on player cooperation rather than point-gaining: it became the first so-called "social" MUD. TinyMUD was inspired by Skrenta's 1988 Monster. Aspnes announced the availability of the first TinyMUD on August 19, 1989; seven months later, on April 29, 1990, he announced TinyMUD's closure (due to the process size exceeding the memory limit of 32 megabytes on the host system).
It's dy-no-mite where you love me I've got the fire that burns to prove just that
Yes it's dy-no-mite where you love me you lit my fuse and blew me off and out
I thought that I was cool calm and elected welcome to the club I thought so too
But I got more charge from you that I expected
Ain't we glad the combination works so good
It's dy-no-mite where you love me...
[ steel ]
I thought it jingles each time you come near me I get all shook up every time we touch
It's gettin' harder every time you left me you know a man can only stand so much
It's dy-no-mite where you love me...
It's dy-no-mite where you love me...