long, baggy knickers for men, introduced before World War I and worn until the 1930s for sports activities, especially golf.
Origin of plus fours
First recorded in 1915–20; so called because four inches are added to the length of ordinary knickers to give the desired looseness
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
men's baggy knickerbockers reaching below the knee, now only worn for hunting, golf, etc
Word Origin for plus fours
C20: so called because the trousers are made with four inches of material to hang over at the knee
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012