What does Boxing Day have to do with boxing?
late 14c., entunen "sing, chant, recite," from Old French entoner "sing, chant" (13c.), from Medieval Latin intonare "sing according to tone," from Latin in- "in" (see in- (2)) + tonus "tone," from Greek tonos (see tenet). A different verb intone was in use 17c.18c., from Latin intonare "to thunder, resound," figuratively "to cry out vehemently," from tonare "to thunder." Related: Intoned; intoning.