What does Boxing Day have to do with boxing?
c.1400, "action of annoying or vexing," from Old French molestacion "vexation, harassing," and directly from Medieval Latin molestationem (nominative molestatio), noun of action from past participle stem of molestare (see molest). It meant "the harassing of a person in his possession or occupation of lands" in Scottish law; in English common law it came to mean "injury inflicted upon another."
late 14c., "to cause trouble, grief, or vexation," from Old French molester "to torment, trouble, bother" (12c.) and directly from Latin molestare "to disturb, trouble, annoy," from molestus "troublesome, annoying, unmanageable," perhaps related to moles "mass" (see mole (n.3)) on notion of either "burden" or "barrier." Meaning "sexually assault" first attested 1950. Related: Molested; molesting.