What does Boxing Day have to do with boxing?
"entertain splendidly," 1650s, from French régaler "to entertain or feast," from Old French regale, rigale, from gale "merriment," from galer "make merry" (see gallant (adj.)). Influenced in Old French by se rigoler "amuse oneself, rejoice," of unknown origin. Italian regalo is from French. Related: Regaled; regaling.