freestyle (n.)youdaoicibaDictYouDict[freestyle 词源字典]
also free-style, 1912, in swimming, in reference to a distance race in which the swimmers may use whatever stroke they choose; 1950 in general use, from free + style. The most common stroke is the front crawl, as this is generally the fastest. As an adjective, from 1957; as a verb, by 1970 (in martial arts).[freestyle etymology, freestyle origin, 英语词源]