downright (adv.)youdaoicibaDictYouDict[downright 词源字典]
c. 1200, "straight down," from down (adv.) + right (adj.1). Meaning "thoroughly" attested from c. 1300. Old English had dunrihte "downwards," and inverted form right-down is attested 17c.[downright etymology, downright origin, 英语词源]