Dosanko, as most Japanese people can tell you, is a word that means "native to Hokkaido." Hokkaido is the northern frontier of Japan, the beautiful (but cold) northernmost island/prefecture of the Japanese archipelago. Japan has been my home since birth, and the greater part of my life has been lived in Hokkaido.
As a non-Japanese living in Japan, I am usually treated with the kind of courtesy one would show a guest. There is an underlying assumption in almost every conversation I have ever had, with all but a handful of people, that I have a "home" in another country, and that I will eventually return there. Which I don't, and I won't. My art name is my way of claiming this as home; claiming a right to claim that I belong here in Hokkaido.
Well, that's one mystery solved, right? The words on the etegami are a quote from the poem The Naming of Cats from the book Old Possum's Book of Practical Cats by T.S.Eliot.