Morgoth.net was first registered to Martin Horner in late November of 1999. It has been a constant source of amusement to him ever since. If the domain was held prior to that time it is unknown to the author.

Why? Why would someone pick the name of the most evil character in all of Tolkien's works to be a domain? And why a .NET TLD instead of the classic .COM (which was very popular at the time)?
 

To answer the first part, it really doesn't matter. Domain names are best when they are short, easy to spell and meaningful. Two out of three, right?
 

The second part is easier, morgoth.net was intended to be an experiment in networking services and functions. The general guidelines of what top level domain to use was boiled quickly down to .NET from elimination. It wasn't a com, org, mil, or edu; there was only one real TLD left.