odds (n.)youdaoicibaDictYouDict[odds 词源字典]
in wagering sense, found first in Shakespeare ("2 Henry IV," 1597), probably from earlier sense of "amount by which one thing exceeds or falls short of another" (1540s), from odd (q.v.), though the sense evolution is uncertain. Until 19c. treated as a singular, though obviously a plural (compare news).[odds etymology, odds origin, 英语词源]