hi-fi (adj.)youdaoicibaDictYouDict[hi-fi 词源字典]
1947, abbreviation of high fidelity (1934), of radio receivers, in reference to their quality of sound reproduction. Hi as an advertiser's phonetic shortening of high is attested by 1914. Fidelity in the sense "faithful reproduction of sound" is from 1878.[hi-fi etymology, hi-fi origin, 英语词源]