A gem backed with foil

⊕To me, a foil foiled: a thing that spoiled, a thing that interfered with the protagonist. That’s the mistake; the verb is a different word entirely (see below). The real etymology is much more comforting (and, to my millennial mind, more like a “heel” in WWE). The foil is the thing that allows the protagonist to shine. The contrast that provides the brilliance.I was browsing wiki-hn and saw “foil” posted. Not heavily upvoted, but I was interested. I wondered which foil was being shared.

It was the literary foil,Oxford English Dictionary, 1st ed. (1901). “Foil, sb.¹” (from Latin folium, leaf), sense 6: “Anything that serves by contrast of colour or quality to adorn another thing or set it off to advantage.” and I found the etymology quite beautiful:

The word foil comes from the old practice of backing gems with foil to make them shine more brightly.

I read more into this and its use in this form was old, and much used by Shakespeare.Onions, C. T. (1911). “foil sb.¹.” A Shakespeare Glossary. Oxford: Clarendon Press. “Setting of a jewel, (hence fig.) that which sets something off to advantage,” cataloguing uses in Richard II, 1 Henry IV, Richard III, Hamlet, and A Lover’s Complaint. In Henry IV, Part 1, Prince Hal promises that his reformation will impress precisely because of the dissolute youth behind it:

And like bright metal on a sullen ground,
My reformation, glittering o’er my fault,
Shall show more goodly and attract more eyes
Than that which hath no foil to set it off.

And in Hamlet he puns it twice over: “I’ll be your foil, Laertes” (Hamlet, 5.2). The literary foil and the fencing foil, in a fencing scene, between two characters who are foils to each other.

An other “foil”

“To foil,” the verb that spoils and frustrates, is a homonym, not a relative. It is from foulerOxford English Dictionary, 1st ed. (1901). “Foil, v.¹”: Old French fouler, “to full cloth, to tread, trample down, press hard upon, crush,” ultimately Latin fullō, a fuller of cloth. The “defeat, frustrate” sense follows in the 1540s. and it entered English as a hunting term: to foil a scent was to spoil the trail by running across it.

So these two foils arrive from opposite directions. One descends from folium, the leaf, and makes the gem shine; the other descends from trampling, and ruins the trail.