I was going to write about a completely different topic when I got stuck on a word for the day before yesterday. In Finnish it's a commonly used word toissapäivä, but I couldn't recall ever coming across a translation of it in English.
Of course that doesn't mean there isn't a word for that. It's just become obsolete and considered archaic. Actually, there is not only one, but two words that can be used to refer to the time two days ago: ereyesterday and nudiustertian.
The former just adding the ere- prefix to yesterday meaning before or earlier while yester- prefix meaning pretty much the same. So it's practically before-before-day.
The later one meaning roughtly as "third day counting backwards from today". This is a bit closer to the Finnish equivalent except we don't count today as ours roughtly translates to "second day backwards".
Of course there are also terms for the other direction, but that I already knew even though I think that's not that commonly used word either. It's also those rare cases when the Finnish translation is literally the same: ylihuominen where yli means over and huominen is morrow.