[[WMG: The islands are what's left of Atlantis.]]
[[spoiler: An ancient civilization]] destroyed by the sea a long time ago. It just makes sense. Ok, so it seems to be on the wrong ocean. But what kind of legend is 100% accurate?
* There's a mythic civilization of Mu supposedly located in the Pacific ocean. Depending on who you ask, it's either separate or synonymous with Atlantis.
[[WMG: Cox is to [[Discworld/NightWatch Carcer]] as [[Discworld/TheColourOfMagic Dr Rijnswand is to Rincewind]].]]
That is, they're alternate-universe analogues of each other.
* ...perhaps suggeting that ''Nation'' and that scene in ''Color of Magic'' actually take place in the same AlternateHistory version of Roundworld?
** Possibly it's the version from the original ''Science of Discworld'', that developed without the elves' assistance and left those differently-spelled signs behind at the space elevator's entry-bays. It's not impossible that the wizards' interactions with early humans in the second book gave the resulting iteration of civilization a different slate of place-names thousands of years later, while incidentally cultivating an unfortunate taste for things like sailfin-crocodile eggs and tree-climbing octopus.
[[WMG: Because Mau didn't get his "man's soul" yet, the 'new' island survived.]]
* Since he ''officially'' didn't have a soul, of course no-one would expect him to behave "normally", as in supporting '''all''' traditions. With so many different groups represented, things should have stayed fragmented for a longer period of time; Mau, however, could bring everyone together (also with enough willpower), and nobody would need to feel offended that he wasn't following any specific traditions; especially since they all ''knew'' him as the "boy with no soul".
[[WMG: The presence of dogs is a hint as to the length of the Nation's history.]]
Dogs are descended from wolves. Species only end up on islands when they have a way to get there.
[[WMG: Daphne's Grandmother Did Kill 138 People]]
* It is mentioned at the start of the book the reason a huge chunk of those people died is they were all at the same party and an infected waiter all served them. That is just close enough to the specific threat of substituting arsenic for sugar at a party to make you wonder. Maybe the old lady saw her opportunity and took it. Pratchett's always written that old ladies can be really ruthless when it comes down to it.