redshirt (v.)youdaoicibaDictYouDict[redshirt 词源字典]
"to withdraw (a player) from the varsity team to add a year to his or her eligibility," 1955, in reference to the red shirts worn by athletes on the scrimmage squad; from red (adj.1) + shirt (n.).[redshirt etymology, redshirt origin, 英语词源]