The concept of the Sword Worlds comes from H. Beam Piper's book _Space_Viking_
(I didn't care much for it, although many of my friends enjoyed it.) It's
a space opera. Many of the names are retained (Gunn, Excalibur, Mithril,
et al) but more are added in Traveller. Most of the other worlds are, of
course, named after swords. Sting, Andruril, Narsil, etc from LOTR, Mjolnir,
etc from Norse mythos; Excalibur, etc from Arthurian legend; and so on.
Hope this is what you were looking for.
Nick Christenson
[email removed]