Q:

Is there a term for words that have a single meaning or are only used in a single context?

Certain words you hear in English are only ever heard in a single context. For example, skirl is used to describe the sound a bagpipe makes. Etymonline generously says the word is "rarely" heard outside that context, but I can't recall ever hearing it used for anything else. I imagine one could use it figuratively to describe another godawful high-pitched screech (sorry, bagpipe lovers), but there's no other bona fide usage for it.
What I want to know is stated in the title of the question: Is there a term for these one-off words? I'm sure there must be, but I can't think of what it might be.
Edit: Judging from some of the head-scratching comments I've received, there seems to be some confusion. Perhaps I did not make my meaning clear. I'm not looking for a word to describe the single instance of skirl. I'm asking about a class of words like skirl. I know there exist other examples of words that are only ever used in one context, but I can't think of any others at the moment.

A:

It's a "stormy petrel." The idea, as described on the linked page, is that (for example) you never (or, at least, rarely) find a petrel that's not stormy. Similarly, "all shrift is short," and lots of other examples. One of the ones there is in fact "every skirl is of bagpipes."

A:

Closely related are fossil words, which have no meaning outside of a certain set phrase.  "Bated" survives only in "bated breath", for example.

A:

There are several terms for closely related concepts:

A nonce word is a word that somebody made up for a localized purpose. Apart from fossilized words, those nonce words that caught on are probably the major part of this group.
A cranberry morpheme is a morpheme that has no meaning on its own, and exists only as part of one or a small number of words. (It's named after the "cran" of "cranberry".) A fossil word is similarly a word that is used only in a small number of phrases (but whose state is specifically due to the original meaning's obsolescence).
A hapax legomenon (of a particular corpus) is a word that appears exactly once.

