Two (2) is another arabic numeral. I guess I had always assumed the reason why the currency sign goes in front of the numbers is because arabic numerals were written and read from right to left. So $5 reads ‘five dollars’ and not ‘dollars five.’ The problem with this hypothesis is that the people who designed ‘arabic’ numerals were Indians who read and wrote left to right. That’s not to say that the Arabic language didn’t have its way with these numerals when the time came, I just don’t know that that’s true.
In Western culture we tend to group things in pairs. Things that don’t occur in multiples of two we call odd. Managing the relationship between opposing pairs is the essence of composition, for what figure could exist if there were no ground?