What does Boxing Day have to do with boxing?
mid-14c., "great-mindedness, courage," from Old French magnificence "splendor, nobility, grandeur," from Latin magnificentia "splendor, munificence," from stem of magnificus "great, elevated, noble, eminent," also "splendid, rich, fine, costly," literally "doing great deeds," from magnus "great" (see magnate) + root of facere "to make" (see factitious). Meaning "greatness, grandeur, glory" in English is from late 14c. That of "beauty, splendor, wealth" is 15c. As one of the Aristotelian and scholastic virtues, it translates Greek megaloprepeia "liberality of expenditure combined with good taste."