Named for the ship that found the first wormhole — which is why it is the line that loops to the front.
Reading the map, Mordecai works from the The Syndicate Logo to the conclusion that one named train has to loop back to the front, probably at a specific station — and finds the party has already discovered it. It is the Escape Velocity line, and he says the name makes it obvious once you know what you are looking for.
The original Escape Velocity was the ship that discovered the wormhole to the first system, where a Gleener scientific crew investigating a Primal ship graveyard came across the Vog Generation Ship. A few hundred cycles later the The Syndicate was formed. The dungeon's rail line carries the name because the named lines are the original worm paths of the galaxy, drawn in miniature.
The exploration ship whose voyage founded the Syndicate, and the rail line named for it.