Something I've noticed over the past couple of days on Tumblr...it seems that fans of Tahno and Tahorra/Tahnorra have all unanimously decided that Tahno's a waterbender from the Foggy Swamp.

I've seen soooo many fics, drabbles, fanart, headcanons, etc. that all promote this idea. Where did it come from, I wonder?
Personally, I think Tahno is a waterbender of mixed Water Tribe and Earth Kingdom origin. It makes sense because: the Foggy Swamp tribe waterbenders were extremely isolated from the rest of the world. Those guys leaving home to travel to an advanced, modern metropolis like Republic City is pretty doubtful. In addition, I've seen way more Earth Kingdom citizens with skin as pale as Tahno's than Foggy Swamp tribesmen (Tahno's skin tone is more similar to that of Toph, Pema, Lin, and Suki than the Foggy Swamp people, who are closer in pigmentation to Jet, Lee, Pipsqueak, Haru, etc.). Also, Earth Kingdom citizens have been seen to have gray eyes, which Tahno has, while I only remember seeing blue and green among the Foggy Swamp tribe, though I may be wrong on that account.
But really, my main points of argument are the skin color and the isolated nature of the Foggy Swamp.