loan (n.) Look up loan at Dictionary.com
mid-13c., from Old Norse lan, related to lja "to lend," from Proto-Germanic *laikhwniz (cognates: Old Frisian len "thing lent," Middle Dutch lene, Dutch leen "loan, fief," Old High German lehan, German Lehn "fief, feudal tenure"), originally "to let have, to leave (to someone)," from PIE *leikw- "to leave" (see relinquish).

The Norse word also is cognate with Old English læn "gift," which did not survive into Middle English, but its derived verb lænan is the source of lend. As a verb, loan is attested from 1540s, perhaps earlier, and formerly was current, but has now been supplanted in England by lend, though it survives in American English.

Loan word (1874) is a translation of German Lehnwort; loan-translation is attested 1933, from German Lehnübersetzung. Slang loan shark first attested 1900.