The inference seems to be that Limsa hired the majority of them (Ul'dah being not too fond of reptilian beastfolk, as it turns out, and Gridania always being a little picky about who is allowed into the Shroud) and possibly Vylbrand being a little closer to Hydaelyn-Mamook than mainland Aldenard is. Limsa certainly has more extensive ports and vessels that go further afield, at any rate, which probably makes travel to and from Mamook easier from Limsa.

As for the name itself, I imagine it's just a carry-over from XI, much like Gysahl or many other terms are. There's probably a Mamook somewhere on Hydaelyn.