Re: Next word: "key"

Herman Miller wrote:
>
> How does one word end up with so many meanings? You've got the metal
> thing that you turn to operate a lock. "Key" has other meanings
> associated with secrets, answers, and so on, which could be related to
> the idea of opening a lock. Then there's a lever or switch on a
> keyboard, which can trigger a musical note to play or a letter to appear
> on your screen. Not to mention the different sorts of levers on wind
> instruments that cover or uncover holes to produce different musical
> notes. And then there's the tonal center of a piece of music, like the
> "key of C minor". And what about those islands in the south of Florida?
In that case, it's an Anglicization of the Spanish _cayo_.

But, certainly, except for the first two, which have a fairly clear
metaphorical extension, it seems rather arbitrary.  I'm wondering if
those are also non-cognates.