Release notes: an unravelled mystery
English has two prefixes spelt un-. UN-1 means ‘not’, ‘the opposite of’, and is most typically used with descriptive adjectives, such as unhappy, while UN-2 means ‘the reverse of’, ‘de-‘, and is typically used with verbs, such as unscrew.
Surprisingly, these word-forming elements are in origin completely unrelated. You can see this by comparing the corresponding prefixes in other Germanic languages. The cousins of UN-1 are very similar; for example German un- and Dutch on-. Those of UN-2 are quite distinct: German ent-, Dutch ont-.
In English, however, the prefixes are not only identical in form, but quite often difficult to distinguish in meaning. The main reason for this is that once you are talking about the past, something that has been reversed is often indistinguishable from something that is the opposite of something else. For example, if you untie (i.e. reverse the tying of) your shoelaces, they can be described as having been untied, but they are also untied because they are not tied.
In the OED there are not a few pairs of adjectives, derived from the two UN- prefixes combined with the past participles of verbs, to which it is often very difficult to reliably assign real-life instances. A good example is unrigged. Unrigged adj.1 means ‘of a ship, etc.: divested of rigging; that has had the rigging taken down’ and is derived from the past of unrig. The following example probably has this meaning since the context describes a process of destruction:
Our shrowds were loose, and our top-masts unrigged (1748)
Equally this example clearly shows unrigged adj.2 ‘of a ship, etc.: not provided with rigging; not yet rigged’, derived from un- plus the adjective rigged:
As all the Iron clads were unrigged the question of bowsprit & headgear did not..apply to them (1866)
But ambiguous examples like the following are quite common:
Warships represented on Geometric vases tend to be shown unrigged, perhaps because the mast and rigging were removed for battle (1993)
Arguably this is ‘not provided with rigging’ but it could be ‘divested of rigging’.
Since UN-1 is a negative prefix, and almost any adjective can be made negative, a further complication can arise when it is desired to make a negative adjective related to a word formed with UN-2, the ‘reversal’ prefix. The two prefixes interfere with one another in such a way that illogical formations appear, in a few cases, even pairs of identical words with opposite meanings.
The normal meaning of unravelled (unravelled adj.1), as one might expect, reflects the past tense of unravel, i.e., ‘that has been disentangled or unwound; made clear, clarified’, as in:
The genuine Skye [terrier],..like an unravelled ball of worsted (1859)
But there is another, more recently formed, word unravelled ( adj.2), nearly always used to describe a mystery, and this means ‘that has not been disentangled or cleared up’:
His background, indeed his philosophy, remain an unravelled mystery (2002)
In theory this could be based on the verb ravel (RAVEL v.1), which, confusingly, can mean either ‘entangle’ or ‘disentangle’. The latter verb is, however, a very rare word in modern English, and the formation seems more likely to have arisen from the familiar verb unravel by some kind of unconscious crossover of interpretation from UN-1 to UN-2, the negative prefix.
The situation is even more striking in the case of the adjective unravellable. Much the older and commoner use of this word is the ‘illogical’ one, ‘incapable of being unravelled; that cannot be disentangled’ (UNRAVELLABLE adj.1); here is the earliest quotation:
We can form no precise Idea of the Manner of its Diffusion thro’ the Nerves, or the unravellable Substance of the Brain (1754)
Whereas UNRAVELLABLE adj.2, meaning (as one would have expected) ‘capable of being unravelled; that can be disentangled’, is comparatively rare, and in some cases is used in such unravellable sentences that one suspects that the author only achieved the ‘logical’ use of the word by accident, e.g.:
No sentence becomes too complex to be grammatically unravellable by the 15-year-old’s awakening intellect (2005)
Ford Madox Ford put his finger on it in 1925:
He got into appalling messes, unending and unravellable—no, she meant un-unravellable!