Knickerbockers were a men's or boys' baggy knee trousers particularly popular in the early twentieth century. Golfers' plus twos and plus fours were trousers of this type. Before World War II, skiers often wore knickerbockers too, usually ankle-length. Until after World War II, in many anglophone countries, boys customarily wore short pants in summer and knickerbockers or "knickers" (or "knee pants") in winter. At the onset of puberty, they graduated to long trousers. In that era, the transition to "long pants" was a major rite of passage. See, for example, the classic song Blues in the Night by Johnny Mercer: "My mammy done told me, when I was in knee-pants, my mammy done told me, son..." Baseball players wear a stylized form of knickerbockers, although the pants have become snugger in recent decades and some modern ballplayers opt to pull the trousers close to the ankles.