Why was "tantrum" trending last week?
1900, a name based on mistranslation of Chinese xenophobic society I-He-T'uan, "Righteous Harmony Band," rendered by British as I-He-Ch'uan "Righteous Uniting Fists," and so associated with the pugilistic boxer.
"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.