Given the dungeon Toto-Rak was from version 1.0, I'm liable to just assume that the 'legendary beast' it was named after never had anything else actually created for it (the fact the lorebook has nothing seems to futher suggest that). 1.0 after all did have a very famously troubled development and launch, and in the general confusion with it's replacement with ARR, Toto-Rak is probably something that got left behind sadly (please prove me wrong though!).

Personally, I think the 'Thousand Maws' part is in itself more just a metaphor and pun on the amount of cells it has inside, given Toto-Rak is, or was, a prison (a literal dungeon for once), which indeed do 'swallow people whole' in a way. But again, that's just my own theory so please take from that what you like.