Other forms: foiled, foils, foiling
Foil is metal rolled so thin it can be torn by hand — the roll in the kitchen drawer that goes over a dish, round a potato, under a grill. British English says tin foil out of habit, though it has been aluminium for eighty years.
The word does three other jobs, and they have nothing to do with each other beyond a shared spelling. To foil a plan is to stop it working, and it is a newspaper verb: police foil robbery. A foil in a story is the character whose flatness makes the hero shine — a jeweller once put bright metal under a gem for exactly that reason, and the sense came straight out of the workshop. And a foil in fencing is the light sword with a blunted tip.
1nounfoilVery thin sheet metal, used in the kitchen for wrapping and covering.
“Cover the dish with foil and put it back in the oven.”
synonyms: tin foil
2verbthwartTo stop a plan or an attempt from succeeding.
“Their escape was foiled by a locked gate.”
3nouncontrastA person or thing whose contrast makes another look better.
“The quiet brother is a foil for the loud one.”
4nounlightA light sword with a blunt tip, used in fencing.
“She competes with a foil rather than a sabre.”
foil is a thin metal sheet.
Also accepted in games: tin foil, aluminum foil
Old French fueille meant a leaf, from Latin folia — so foil is a metal leaf, which is what a sheet of it looks like when it catches the light. The same Latin gives us foliage and portfolio, a case for carrying leaves of paper.
Proto-Indo-European
*bʰleh₃-
Latin
folia
Old French
fueille — plant leaf
Middle French
fueille
Middle English
foyle
English, today
foil
From Middle English foyle, from Middle French fueille, from Old French fueille (“plant leaf”), from Latin folia, the plural of folium, mistaken as a singular feminine. The literary sense is from the practice of backing a gem with metal foil to make it shine more brilliantly. a doublet of folio and folium, distantly also with a doublet of phyllo and phyllon.
Etymology from Wiktionary, CC BY-SA
Practised in Colors, Shapes & Numbers, Containers & Packaging