In TC&tC p. 177f The Roof of the World Janaindar (p.178 box Ruq Story Seeds) is presented as a place in the Hindu Kush as told by legends of nomads in the valleys below. "Jana Indar" is Hindi for "enter" or "going in".
You would likely need to look for modern retellings of their medieval legends - and I have no books about these at hand. TC&tC has a list of books about Myths and Legends in the back. What about ordering "Fabled Cities, Princes and Jinn from Arab Myths and Legends (World mythology series)" listed there?
I think of tales like the South Tyrolean ones about the rose garden of King Laurin.
Well, sure, that King Lauren the Dwarf stuff is E481.4. Beautiful land of dead. (Rosengarten). in Aarne-Thompson.
My problem is that the bibliography in Cradle and Crescent lists some solid sources, from Jack Zipes to several Arabian Nights books. But it also lists DC's Sandman and Fables comics, which I don't own and aren't available at my library. They used to be, but the years since 2020 have wrought sad changes.
I suspect Janaindar was made up by a comic book author, but sometimes comic book authors take things from their own research. Only comic books don't have bibliographies. Normally.
Also, Janaindar could be a variant spelling or an artistic conceit for the sourcebook.
The book's author lists Janaindar as a topic waiting to get a longer treatment on his blog, so maybe we can all ask him nicely to get to it sooner rather than later --
Although... Jarkman is an old name for a counterfeiter and there's a bunch of T2K stuff? Well, I don't know much about game publishers, and it's something to look into, at least.