Is it farther or further?
early 14c., of uncertain origin. One theory connects it with Latin stuprata, fem. past participle of stuprare "have illicit sexual relations with," or Late Latin strupum "dishonor, violation." Others suggest Middle Dutch strompe "a stocking," or strompen "to stride, to stalk" (as a prostitute might a customer). The major sources don't seem to give much preference to any of these. Weekley notes "Gregory's Chronicle (c.1450) has streppett in same sense." In 18c.-early 19c., often abbreviated as strum and also used as a verb, which led to some odd dictionary entries:
TO STRUM: to have carnal knowledge of a woman, also to play badly on the harpsichord or any other stringed instrument. [Capt. Francis Grose, "A Classical Dictionary of the Vulgar Tongue," 1796]