Bargain likely traces to a Frankish word for borrowing and pledging — the Germanic tribes left their commercial vocabulary embedded deep in the French language.
An agreement between parties fixing terms of a transaction. Also something acquired at a lower price than expected, or a verb meaning to negotiate terms.
From Old French bargaignier (to haggle, negotiate), possibly from Frankish *borganjan (to lend, borrow) or a related Germanic source, ultimately perhaps from Proto-Germanic *burgōną (to pledge, guarantee) Key roots: *borganjan (Frankish: "to lend, borrow"), *burgōną (Proto-Germanic: "to pledge, guarantee").
Bargain may descend from a Frankish word meaning "to borrow" — the Germanic tribes who settled in France left their commercial vocabulary embedded in the French language. The phrase "into the bargain" (meaning "in addition, as a bonus") dates to the 16th century. The concept of a "Faustian bargain" — a deal with the devil trading long-term consequences