late 14c., from French
galaxie
or directly from Late Latin
galaxias
"the Milky Way" as a feature in the night sky (in classical Latin
via lactea
or
circulus lacteus
), from Greek
galaxias
(adj.), in
galaxias kyklos
, literally "milky circle," from
gala
(genitive
galaktos
) "milk" (from PIE root
*g(a)lag-
"milk").
The technical astronomical sense in reference to the discrete stellar aggregate including the sun and all visible stars emerged by 1848. Figurative sense of "brilliant assembly of persons" is from 1580s.
Milky Way
is a translation of Latin
via lactea
.
See yonder, lo, the Galaxye Which men clepeth the Milky Wey, For hit is whyt. [Chaucer, "House of Fame"]
Originally ours was the only one known. Astronomers began to speculate by mid-19c. that some of the
spiral nebulae
they could see in telescopes were actually immense and immensely distant structures the size and shape of the Milky Way. But the matter was not settled in the affirmative until the 1920s.