doubloon (n.) Look up doubloon at Dictionary.com
1620s, from French doublon (16c.) and directly from Spanish doblon a gold coin, augmentative of doble "double" (coin so called because it was worth twice as much as the Spanish gold pistole), from Latin duplus "twofold, twich as much" from duo "two" (from PIE root *dwo- "two") + -plus "more" (see -plus). Also see -oon.