Why is the ninth month called September?
1590s, agmarine, "bluish-green type of beryl," from French or Provençal, from Latin aqua marina "sea water," from aqua "water" (see aqua-) + marina, fem. of marinus "of the sea" (see marine (adj.)). Apparently first used as a description of a bluish-green color by John Ruskin, 1846. Abbreviation aqua is attested from 1936.