Jockey-strap in the same sense is from 1890, with also an example from 1870 but the sense is uncertain.” The term underwear means, “clothing worn under other clothes, typically next to the skin”. According to Etymonline, “1850, probably one of the many colloquial uses of Jock the northern and Scottish form of Jack, which was used generically for 'common man' from c. The term jockstrap means “support or protection for the male genitals, worn especially by sportsmen.” If you take a look at the history of the term, it was coined in 1887, 'supporter of the male genital organs, used in sports”.
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