The freedom that knickerbockers allowed led to the use of Plus fours for golf in the early 20th century. Since these baggy leggings required an extra four inches of material to allow for the overhang of the leg-band they got the name ‘plus-fours’ or 'plus fours'.
Similarly, the commonly used plus-twos (as worn by the shooting fraternity) required two inches more of material.
There were even plus-eights - which can be seen at Trevira's phtostream.
