Just the other month

I was just reading something I wrote the other day which contained the phrase, "the other day."  That's one of those English idioms that is generally understood although it doesn't make a lot of sense.  But that's pretty much what an idiom is, I guess.

Taken literally -- not advisable with idioms but something I absolutely love to do anyway -- that would mean there are actually only four available days:  yesterday, today, tomorrow, and the other day.  Well, no -- I'm wrong.  We do also have the day before yesterday and the day after tomorrow.

So, when exactly was the other day?

There are some lively debates on the Internet about it.  It appears to be universally agreed that the other day was a recent day, but there are those who wish actually to assign a specific number of days to it, three days being particularly popular among them.

That could work according to our collection of available days -- yesterday is one day ago, and the day before yesterday is two days ago, so the other day could be three days ago.  But what about four or five days ago?  And if we get to six days ago, we are treading dangerously close to last week.

I begin to wonder if there is an etymological link between idiom and idiot.