What does Boxing Day have to do with boxing?
early 15c., from Middle French pernicios (13c., Modern French pernicieux) and directly from Latin perniciosus "destructive," from pernicies "destruction, death, ruin," from per- "completely" (see per) + necis "violent death, murder," related to necare "to kill," nocere "to hurt, injure, harm," noxa "harm, injury" (see noxious). Related: Perniciously; perniciousness.
pernicious per·ni·cious (pər-nĭsh'əs)
Tending to cause death or serious injury; deadly.