Kuvirr Morri was a Jedi Consular living nearly six thousand years before the birth of Malak. It was the time known as the Coming of the Jedi Republic. Morri was one of the first seven Jedi to lead the authoritative view that was the Republic. It wasn't until the invasion of the Dagobrasen invaders arrived that Morri left the Jedi Order because the Jedi didn't take immediate action against the Dagobrasen.
The Jedi took the way of the Negotiator and were nearly slaughtered by the Dagobrasen because of it. Morri took action and began a new organization known as The New Sith Order. The Jedi disagreed with this new order and took action against they're own bretheren.
Now Morri had two enemies to deal with... the Jedi and the Dagobrasen. This was a time when there were no lightsabers and the Force was well misunderstood. So, of course, all Hell broke loose.
Morri wound up overrunning the Jedi and exiling the remaining evil Dagobrasen invaders to planet Havik V, that would soon be renaimed Dagobah, for it's now strange and disfigured inhabitants. Morri renamed himself after the Sith, in which, at the time, seemed to be the main role of leadership in the Galaxy, to Darth Sinirik. The term "Darth" at the time, wasn't a term at all, Sinirik actually used it as his first name, in homage, all of his successors used "Darth" as their first name once thay became an official officer of the Sith.