“Twenty is perhaps the oldest, most natural large number for mankind to relate to, for it is the number we achieve by counting up all our fingers and toes. Echoes of this unit (called Vigesimal) can still be found in both the French and English language. The French still express eighty as ‘quatre-vingts’ (four twenties), while English keeps a special word (‘score’) for this number, as in the expression ‘four score and ten.’ And until decimalization was introduced in 1971 the English monetary unit was still so ordered, with twenty shillings to the pound.”
Excerpted from: Rogerson, Barnaby. Rogerson’s Book of Numbers: The Culture of Numbers–from 1,001 Nights to the Seven Wonders of the World. New York: Picador, 2013.