It's a crushing, built-in disappointment - as well, of course, as being hideous.
Sandwich compound is rather similar. A sandwich compound should, obviously, consist of something unctuously delicious, like mayonnaise or maple syrup; tabasco or tzatziki; soured cream or creme fraiche.
And what is it?
It's an organometallic compound.
That one is called ferrocene.
What are sandwich compounds for?
Well, apparently they make internal combustion engines work more smoothly. And they're useful when making plastics.
I expect we'd miss them if they weren't there, but, I mean, sandwich compound...it leaves you just salivating for a dollop of Rose Marie sauce, doesn't it.
Like I said: vicious.
Phrasal noun Not To Use Today: sandwich compound. The sandwich is named after John Montague, 4th Earl of Sandwich, who ate sandwiches rather than leave the gambling tables for proper meals. Compound is from the Old French compondre to collect or set in order, from the Latin compōnere.