Boxer briefs sometimes spelled boxerbriefs or called tight boxers are a hybrid type of men's undergarment which are long in the leg, similar to boxer shorts , but tight-fitting like briefs. They emerged as a style in the s and are commonly worn for sports and as every-day underwear. Depending on the manufacturer, boxer briefs may also be spelled as one word. They are sometimes called " trunks " in the United Kingdom and Australia. Boxer briefs are commonly thought to have been pioneered by designer John Varvatos during his — stint at Calvin Klein as head of menswear design.