cod-piece (n.)

c. 1200, pece, "fixed amount, measure, portion;" c. 1300, "fragment of an object, bit of a whole, slice of meat; separate fragment, section, or part," from Old French piece "piece, bit portion; item; coin" (12c.), from Vulgar Latin *pettia, probably from Gaulish *pettsi (compare Welsh peth "thing," Breton pez "piece, a little"), perhaps from an Old Celtic base *kwezd-i-, from PIE root *kwezd- "a part, piece" (source also of Russian chast' "part"). Related: Pieces.

Meaning "separate article forming part of a class or group" is from c. 1400; that of "specimen, instance, example" is from 1560s. Sense of "portable firearm" is from 1580s, earlier "artillery weapon" (1540s). The meaning "chessman" is from 1560s. Meaning "a period of time" is from early 14c.; that of "a portion of a distance" is from 1610s; that of "literary composition" dates from 1530s.

Piece of (one's) mind "one's opinion expressed bluntly" is from 1570s. Piece of work "remarkable person" echoes Hamlet. Piece as "a coin" is attested in English from c. 1400, hence piece of eight, old name for the Spanish dollar (c. 1600) of the value of 8 reals and bearing a numeral 8. Adverbial phrase in one piece "whole, undivided, without loss or injury" is by 1580s; of a piece "as of the same piece or whole" is from 1610s.

large sea fish, edible and widely distributed in colder seas, mid-14c. (late 13c. in a surname, Thomas cotfich), of unknown origin; despite similarity of form it has no conclusive connection to the widespread Germanic word for "bag" (represented by Old English codd, preserved in cod-piece). Codfish is from 1560s. Cod-liver oil, known at least since 1610s, was recommended medicinally from 1783 but did not become popular as a remedy until after 1825.