What does Boxing Day have to do with boxing?
c.1400, instruccioun, "action or process of teaching," from Old French instruccion (14c.), from Latin instructionem (nominative instructio) "building, arrangement, teaching," from past participle stem of instruere "arrange, inform, teach," from in- "on" (see in- (2)) + struere "to pile, build" (see structure (n.)). Meaning "an authoritative direction telling someone what to do; a document giving such directions," is early 15c. Related: Instructions.