What does Boxing Day have to do with boxing?
late 14c., from Anglo-French wafre, Old North French waufre "honeycomb, wafer," perhaps from Frankish (cf. Flemish wafer, altered from Middle Dutch wafel "honeycomb;" see waffle (n.)). Also found in Old French as gaufre, gofre "wafer, waffle." Eucharistic bread first so called 1550s.
thin cakes (Ex. 16:31; 29:2, 23; Lev. 2:4; 7:12; 8:26; Num. 6:15, 19) used in various offerings.