score (n.) late Old English scoru "twenty," from Old Norse skor "mark, notch, incision; a rift in rock," also, in Icelandic, "twenty," from Proto-Germanic *skur-, from PIE root

PIE root

*kā-, Proto-Indo-European root meaning "to like, desire." It forms all or part of: caress; charity; cherish; Kama Sutra; whore; whoredom.

› word

*sker- (1) "to cut." The notion probably is of counting large numbers (of a passing flock of sheep, etc.)

Why is 20 known as a score?

Shepherds would often count their sheep by making a notch in a piece of wood for every 20 sheep, from which the meanings "a score"="twenty" and "score" = "tally" both arise.

Does a score equal 20?

A 'score' is a group of 20 (often used in combination with a cardinal number, i.e. fourscore to mean 80), but also often used as an indefinite number (e.g. the newspaper headline "Scores of Typhoon Survivors Flown to Manila").