Everybody knows what butter is. You agitate cream sufficiently and the little globs of fat come out and stick together and then you spead that all over bread or fry in it. That's butter.

I have a jar of what I would call "preserves" which declares itself, on the label, to be "fruit butter." The hell you say!? In what sense can fruit make butter?

If the etymology of the word "butter" is all about cows and cheese (which I think it is), then how does one get from those word origins to a smear of mushed raspberries?