Why is "elsewhen" not a proper word?
Elsewhere is an amazing word, as you can refer to other places very easily. What about elsewhen? Does such an equivalent of elsewhere for time exist? For example:
"Fertility might have fallen among women born between 1940 and 1960, and remained unchanged elsewhen."
Would that be an example of an appropriate use of that word, if it were to exist? If not, is there an alternative, easier way to say elsewhen, so that its existence has been unnecessary?
Elsewhen did exist in English; the OED has several entries, the most recent from 1570, the earliest from 1418:
Or ellys whan quan hem lest to remeve þens.
There are also entries for elsehow, elsewhat, elsewhence, elsewhither, and elsewho, plus elsewards and elsewise, and like elsewhen, all are marked as obsolete. The location-related words seem to have survived the longest, with elsewhence and elsewhither persisting into the 19th century and regionally, and of course elsewhere remaining in common usage.
Why those words fell out of fashion is hard to say, of course. Perhaps English speakers had more use for words for other locations than for other times— in the same way, we have anywhere and everywhere, but anywhen and everywhen are at best non-standard. On the other hand, we also lost otherwhere, except in some dialects, perhaps those which still use otherwhat and othersome and otherward; the OED doesn't specify.
In the situation you propose, the only single word I would have applied is otherwise, a highly flexible word that simply means in some additional or different way— another time, another place, another manner. Or, you could always be explicit and say at other times or in other years or other than this period.
There actually is, or perhaps better said was, such a word in the adverb othertimes. However, the OED says that othertimes is now obsolete. It was not uncommon in Early Modern English up through the 18th century, but its use declined during the first half of 19th century. It tends to oppose sometimes.
Democritus would sometimes say that the images and their circuitions were Gods, and othertimes this Nature, which disperseth these images, and then our knowledge and intelligence. (Essays of Michael Lord of Montaigne)
The first appearances were, a low state of health, depressed, exhausted, and sallow look — the eyes sunken, sometimes of glossy whiteness, othertimes icteric, with dark areolae around — nose pinched — mouth blanched — except where ... (Researches on Primary Pathology: And the Origin and Laws of Epidemics)
As often as the Devil appeared to the Mexicans, they made immediately an idol of the figure in which they bad seen him ; sometimes as a lion, othertimes as a dog, othertimes as a serpent ; and as the ambitious Devil took advantage of this ... (The Poetical Works of Robert Southey)
This adverb eventually came to be used as a noun serving as a prepositional object for in and at, and finally people gave up and wrote a space between the two words:
- at other times
- in other times
Which is where we stand today. People may well ask “why” something did or did not happen in language, but most such questions have no possible concrete answer.
The historical record shows many combinations with any, other, some, when, time, times that are now rarely seen. Combining the old ones with the extant ones, and disregarding hyphens, the list of such adverbs is very long:
aforetime, anyplace, anyway, anyways, anywhen, anywhence, anywhere, anywhither, anywise, beforetime, betimes, daytimes, elsehow, elsewards, elsewhat, elsewhen, elsewhence, elsewhere, elsewhither, elsewho, elsewise, everywhen, foretime, heretoforetime, midtime, mostwhen, noontimes, nowhen, oftentime, oftentimes, otherlike, otherliker, othertime, othertimes, otherward, otherwards, otherways, otherwhat, otherwhence, otherwhere, otherwheres, otherwhile, otherwhiles, otherwhither, otherwise, overtime, sometime, sometimes, someway, someways, somewhat, somewhatly, somewhen, somewhence, somewhere, somewhile, somewhiles, somewhither, somewho, somewhy, somewise, toforetime.