I had a student moaning because I insisted he say twice and not "two times". And he asked "But why?" to which I replied, "Because that’s how you say it!"
However on reflection, his question was a valid one.
In Latin there doesn’t appear to be any discernible pattern
- once is semel
- twice is bis
- thrice is ter
- four times is quater
- five times is quinquies
but in German the suffix -mal is used,
- once is einmal
- twice is zweimal
- thrice is dreimal
- four times is viermal
In French the term fois is repeated
- once is une fois
- twice is deux fois
- thrice is trois fois
- four times is quatre fois
In Italian the noun volta (s) volte (p) is used
- once is una volta
- twice is due volte
- thrice is tre volte
- four times is quattro volte
In Spanish veces is repeated
- once is una vez
- twice is dos veces
- thrice is tres veces
- four times is cuatro veces
And all the following languages follow the same pattern. In Danish it’s gange; in Norwegian ganger; in Polish raz and razy; Portuguese has vez and vezes; and Welsh uses waith and gwaith.
- So why does the English language have three different words for "one time", "two times" and "three times"?
- Beyond a shadow of a doubt the English thrice is doomed to exile if not extinction; will twice suffer the same fate? For instance, many Italian speakers learning English do say "two times"—for them it makes more sense.
I am not suggesting that twice is old fashioned, unnecessary or— heaven forbid—nonsensical. But considering the history of thrice, it is possible that sometime in the future, native speakers will look back fondly on twice as being quaint and quite rare. My second question is in fact asking if there are signs of this happening now.
The reason English has three different words for those is because English has three different words for 1, 2, and 3. It’s like why we have three different words for sixth, eighth, and twelfth: there’s a suffix here used with regular numbers.
The difference is that instead of ‑th for ordinals, it’s ‑ce for adverbials, and you just aren’t recognizing that ‑ce adverbs things — or at least, that it adverbed them once upon a time.
That’s because ‑es was a genitive adverbial suffix in Old English. You can see its remains in all kinds of adverbs that are today spelled with an ‑s at the end.
Note that genitive nouns also end in ‑s. The difference is that making genitive nouns (well, and noun phrases with a clitic ‑’s) is still productive. However, making adverbials this way no longer is so, although now and then people coin new ones along existing models by analogy.
Other ‑s examples of adverbs made like once, twice, thrice include such words as afterwards, backwards, besides, betimes, forwards, hereabouts, needs, nowheres, nights, nowadays, sideways, thereabouts, towards, unawares — with plenty more where those came from. As Janus mentions in comments, there is also a broad set of those which gained a parasitic (=inorganic, non-etymological) final ‑t on top of their ‑es/‑s, such as acrost, against, amidst, amongst, betwixt, gainst, whilst.
Because we made adverbs out of things by adding ‑es (later ‑s) all the time, it was the natural way to make an adverbial out of the numbers. The word nonce has the same origin, although that’s used for a noun not an adverb. In Old English, the word for modern once was ænes or enes, genitive forms coming directly from the Old English word for one, which was án.
By the way, the Old English word án that gave birth to modern one and once also gave us the indefinite articles a, an. But when Old English speakers said ænes (again, that was their word for once), it had two different syllables. That situation was not to last, however, and this led to orthographic changes.
Middle English picked up twice and thrice by the same construction, although with differing spelling and pronunciation than we use today. Then around 1500, as ones became monosyllabic, it began to be spelled -ce to indicate the lack of voicing — and, for the cases of twice and thrice, to indicate a change in character of the preceding vowel.
So what’s going on is that you no longer recognize this fossilized morpheme as meaningful. It means exactly the same thing as those other free morphemes you mention in other tongues.
And no: twice isn’t going away. Neither are twin, both, halve, or double. Twain might someday be, though, moving into literary use not bar talk. As for your Italian learners, I strongly advise against saying “two times”; it does not sound right to this native ear. Indeed, the OED specifically reports that twice is:
In all senses now the regular substitute for the phrase two times
On the other hand, tuppence and thruppence are hardly worth a farthing today, eh? 🙂