tinfoil (n.)

Old English tin, from Proto-Germanic *tinom (source also of Middle Dutch and Dutch tin, Old High German zin, German Zinn, Old Norse tin), of unknown origin, not found outside Germanic.

Other Indo-European languages often have separate words for "tin" as a raw metal and "tin plate;" such as French étain, fer-blanc. Pliny refers to tin as plumbum album "white lead," and for centuries it was regarded as a form of silver debased by lead; hence its figurative use for "mean, petty, worthless." The chemical symbol Sn is from Late Latin stannum (see stannic).

Meaning "container made of tin" is from 1795. Tin-can is from 1770; as naval slang for "destroyer," by 1937. Tin-type in photography is from 1864. Tin ear "lack of musical discernment" is from 1909. Tin Lizzie "early Ford, especially a Model T," first recorded 1915.

"very thin sheet of metal," early 14c., foile, from Old French foil, fueill, fueille "leaf; foliage; sheet of paper; sheet of metal" (12c., Modern French feuille), from Latin folia, plural (mistaken for fem. singular) of folium "leaf" (from PIE root *bhel- (3) "to thrive, bloom").

The sense of "one who enhances another by contrast" (1580s) is from the practice of backing a gem with metal foil to make it shine more brilliantly. The meaning "light sword used in fencing" (1590s) could be from this sense, or from foil (v.). The sense of "metallic food wrap" is from 1897.