TinyMUD

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.