What does Boxing Day have to do with boxing?
mid-15c., "medical skill; a medicinal compound," from Middle French médicament (15c.), from Latin medicamentum "drug, remedy," literally "means of healing," from medicare "to heal, cure" (see medication).
medicament me·dic·a·ment (mĭ-dĭk'ə-mənt, měd'ĭ-kə-)
An agent that promotes recovery from injury or ailment; a medicine.