Rarther oddly, the centre of the trading confederation is on Procyon, which we're told is a Vulcan name (??) and according to the Star Trek Star Charts is actually Andoria, even though it obviously isn't here (although IIRC, Shane Johnson said Andor was Epsilon Indii in Worlds of the Federation)
The star's name is Epsilon Indi. That's the possessive form of the name of the constellation
Indus. A lot of people who didn't take Latin in school mistakenly assume that the plural or possessive of -us is -ii, because they're confusing it with plurals/possessives of words ending in -ius (e.g. radius/radii). If the word ends in -us, then it's just -i.
And
The Worlds of the Federation is not the original source for that proposal, not by a long shot. TWotF was a latter-day work that borrowed a lot of pre-existing ideas from fandom, and I get so tired of the modern tendency to assume that Shane Johnson is the original source for things like this. It was Franz Joseph's
Star Fleet Technical Manual that first included Epsilon Indi as a founding system of the Federation, and it was Eileen Palestine & Geoffrey Mandel's
Star Fleet Medical Reference Manual that first identified Eps Indi with Andor (as did Mandel's later
Star Trek Maps, a source that TwotF drew on quite heavily). Mandel clearly changed his mind by the time of
Star Trek Star Charts, probably because Procyon fit better with the spatial relationship between Vulcan and Andoria suggested in ENT.
Procyon, of course, is Greek, meaning "before the Dog" (because of its proximity to Sirius in Canis Major, the "Dog Star"). I'm reminded of how "Broken Bow" treated Rigel as an alien name that the human characters had never heard before reading it in the Vulcan star charts.
