Word Origin of the Day: Score (for 20)

I recently used the word "scores" to indicate a number less than hundreds, but more than 15 or so.

Then I wondered why we call "20" a "score."

I thought it might be from "game score"—some game where the increment was 20 (like 6 for football and 15 for tennis).

But no, it is from another meaning of score: to make a mark, as in a cut or scratch on a surface. 

So in tallying something, ancient people would mark a stick or something at every 20 items: score!