What does Boxing Day have to do with boxing?
mid-14c., "return to health," from Anglo-French recoverie (c.1300), Old French recovree "remedy, cure, recovery," from past participle stem of recovrer (see recover). Meaning "a gaining possession by legal action" is from early 15c. That of "act of righting oneself after a blunder, mishap, etc." is from 1520s.