The Norse word also is cognate with Old English læn "gift," which according to OED did not survive into Middle English, but its derived verb lænan is the source of lend (v.). From early 15c. as "a contribution to public finances" (ostensibly voluntary but often coerced; sometimes repaid, sometimes not). As a verb, loan is attested from 1540s, perhaps earlier, and formerly was current, but it has now been supplanted in England by lend, though it survives in American English. Slang loan shark first attested 1900 (see shark (n.)).
c. 1400, "engage in business transactions, discuss or arrange terms of a transaction; to vend or sell," from Old French bargaignier "to haggle over the price" (12c., Modern French barguigner), perhaps from Frankish *borganjan "to lend" or some other Germanic source, ultimately from Proto-Germanic *borgan "to pledge, lend, borrow" (source also of Old High German borgen; Old English borgian; from PIE root *bhergh- (1) "to hide, protect;" compare borrow).
Diez and others suggest that the French word comes from Late Latin barca "a barge," because it "carries goods to and fro." There are difficulties with both suggestions. Related: Bargained; bargaining. To bargain for "arrange for beforehand" is from 1801.