John Cowan wrote
> 2) "Most important part". Here we have the keystone, the top stone of
> the arch which holds it in place. "Key idea" is another example of this.
> "Key" is also applied to cotter pins, probably by analogy with keystones.
> Finally we have the "key", or free-throw area, in basketball.
I note that "keystone" would be "kop warski" in Lindiga. I bring this up
because "kop" was already the word for "stone" or "rock", and the
resemblance to "Keystone Kops" is entirely coincidental! (In any case,
this phrase would likely be pronounced as a unit, in which case it'd be