galleon (n.) Look up galleon at
kind of large ship, 1520s, from French galion "armed ship of burden," and directly from Spanish galeón "galleon, armed merchant ship," augmentative of galea, from Byzantine Greek galea "galley" (see galley) + augmentative suffix -on. Developed 15c.-16c., it was shorter, broader, and with a higher stern superstructure than the galley. In English use, especially of Spanish royal treasure-ships or the government warships that escorted private merchant ships in the South American trade.
GALLEON. The accepted term for the type of ship which the Spaniards used in 1588; that is, an armed merchantman of exceptional quality, combining the strength of the mediaeval trader with some of the finer lines and fighting features of the GALLEY. [Sir Geoffrey Callender, "Sea Passages," 1943]
Italian agumented form of galea, galeaza, led to a different 16c. ship-name in English, galliass (1540s).