The term "cosmism" seems to have originated with the Russian Cosmists, in the mid-1800's.
The most famous Russian Cosmist was Konstantin Tsiolkovsky, who according to Wikipedia
believed that colonizing space would lead to the perfection of the human race, with immortality and a carefree existence. He also developed ideas of the "animated atom" (panpsychism), and "radiant mankind".
All this is generally conceptually harmonious with my use of the term here, though not precisely identical.
My friend and colleague Hugo de Garis has used the term Cosmist to refer to (again quoting the mighty Wikipedia)
a moral philosophy that favours building or growing strong artificial intelligence and ultimately leaving the planet Earth.... Cosmists will foresee the massive, truly astronomical potential of substrate-independent cognition, and will therefore advocate unlimited growth in the designated fields, in the hopes that "super intelligent" machines might one day colonise the universe. It is this "cosmic" view of history, in which the fate of one single species, on one single planet, is seen as insignificant next to the fate of the known universe, that gives the Cosmists their name.
Again this is generally harmonious with my use of the term here, though not precisely identical.
Different people have used the term Cosmism with different shades of meaning, but we're all pushing in the same general direction!