boxershorts

Boxer shorts

(also known as

loose boxers

or as simply

boxers

) are a type of undergarment typically worn by men.
 
The term has been used in English since 1944 for all-around-elastic shorts, so named after the shorts worn by boxers, for whom unhindered leg movement ("footwork") is very important. Boxers come in a variety of styles and design but are characterized by their loose fit.