shoo-in (n.)youdaoicibaDictYouDict[shoo-in 词源字典]
"easy winner" (especially in politics), 1939, from earlier sense "horse that wins a race by pre-arrangement" (1928); the verb phrase shoo in in this sense is from 1908; from shoo (v.) + in (adv.).[shoo-in etymology, shoo-in origin, 英语词源]