What does Boxing Day have to do with boxing?
obsolete except in place names, Old English næs "a promontory," related to nasu "nose" (see nose (n.)). Cognate with Old Norse nes, Danish næs, Swedish näs, Middle Dutch nesse.
word-forming element denoting action, quality, or state, attached to an adjective or past participle to form an abstract noun, from Old English -nes(s), from West Germanic *in-assu- (cf. Old Saxon -nissi, Middle Dutch -nisse, Dutch -nis, Old High German -nissa, German -nis, Gothic -inassus), from *-in-, noun stem, + *-assu-, abstract noun suffix, probably from the same root as Latin -tudo (see -tude).