Origin of once again

I'm sure that most of you will be familiar with the phrase "once again."

Once again, I take that back.

However, I don't get the words. Once means "one time." However, again means that you did it again. Isn't this phrase an oxymoron?

Solution 1:

I think OP is being more than a bit "literal" in seeing a conflict between once and again here.

In this context, the word once is largely superfluous. But if it has any significance at all, it's just an intensifier for again. It could, for example, be used repeatedly within the same discourse, applying to the same action/statement. This has the effect of calling attention to the repetition.

There's no implication there was only a single preceding instance - once just means "in the past", or "previously" there was at least one occurrence of the action, which is now being repeated again.

Solution 2:

Once again means "one more time."

The meaning of a phrase is not necessarily the sum of the meaning of the single words; for example, once or twice doesn't mean "or it's one time, or it's two times"; it means "a few times."

Set phrases do have a meaning that cannot be understood reading the meaning of the single words used in the phrase. You don't get the meaning of man of the cloth by looking at the meaning of man, of, and cloth.