I had a student moaning at me 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 iterum
• 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, is twice suffering the same fate? For instance, many Italian learners do say "two times"—it makes more sense.

Related Questions:
Why has the word “thrice” fallen out of common usage?
Twice vs Two Times
Is there a word for four times as much, analogous to once, twice, and thrice?