What does Boxing Day have to do with boxing?
mid-12c., from Old French covrir (12c., Modern French couvrir) "to cover, protect, conceal, dissemble," from Late Latin coperire, from Latin cooperire "to cover over, overwhelm, bury," from com-, intensive prefix (see com-), + operire "to close, cover" (see weir). Related: Covered; covering. Military sense is from 1680s; newspaper sense first recorded 1893; use in football dates from 1907. Betting sense is 1857. OF horses, as a euphemism for "copulate" it dates from 1530s. Covered wagon attested from 1745.
early 13c., in compounds, from cover (v.). Meaning "recording of a song already recorded by another" is 1966. Cover girl is U.S. slang from 1915, shortening of magazine-cover girl.