boxeryoudaoicibaDictYouDict[boxer 词源字典]
boxer: [15] Boxer is a much travelled word. In its original sense ‘fighter’ it comes of course from the verb box, the origins of which remain mysterious. German borrowed the name for a new breed of dog, a sort of elongated, more elegant version of a bulldog – presumably either in tribute to its supposed pugnaciousness or because its flattened nose looked like that of an unsuccessful boxer.

Then in the 1930s English acquired this new application back from German. The use of ‘Boxer’ for the Chinese rebels around the turn of the 20th century who attempted to drive out all foreigners is based on their Chinese name, yi hé quán, literally ‘righteous harmonious fists’.
[boxer etymology, boxer origin, 英语词源]
boxer (n.)youdaoicibaDictYouDict
"fighter," late 15c., agent noun from box (v.2). The name of the breed of dog (1934), is from German (the breed originated in Germany), itself taken from English boxer "fighter;" the dog so called for its pugnaciousness. Boxer shorts (1943) so called from their resemblance to the attire worn in the ring.