The word "Rythulains" is mentioned in the Developer Commentary in Journey Collector's Edition, it is used (albeit jokingly) as a name for the species that all of the travelers are comprised of. Despite it's origin, it has been used as a term to describe them in fan-works.

Rythulians are humanoid creatures covered in cloth normally in red or white, and with a black face or mask with eyes of pure white. Other features are speculative and might vary from artist to artist.