What does Boxing Day have to do with boxing?
"the human race," c.1300, earlier man-kende (early 13c.), from man (n.) + kind (n.). Replaced Old English mancynn "human race." Also used occasionally in Middle English for "male persons" (late 14c.), but otherwise preserving the original gender neutrality of man (n.). For "menfolk, the male sex," menkind (late 14c.) and menskind (1590s) have been used.