What does Boxing Day have to do with boxing?
Old English spurnan "to kick (away), reject, scorn, despise," from Proto-Germanic *spurnanan (cf. Old Saxon and Old High German spurnan, Old Frisian spurna, Old Norse sporna "to kick"), from PIE root *spere- "ankle" (cf. Middle Dutch spoor "track of an animal," Greek sphyron "ankle," Latin spernere "to reject, spurn," Sanskrit sphurati "kicks," Middle Irish seir "heel"). Related: Spurned; spurning.