Old English Gota (plural Gotan) "a member of the Germanic people who lived in Eastern Europe c.100 C.E.," from Late Latin Gothus (plural Gothi), from Greek Gothos (plural Gothoi), from Gothic *Gutos, which is preserved in Gothic gutþiuda "Gothic people," the first element cognate with Old Norse gotar "men" (the second meaning "people; see Dutch). "The sense 'men' is usually taken to be the secondary one, but as the etymology of the word is unknown, this is uncertain" [Gordon]. The unetymological -th- in the modern English word is from Late Latin.
They entered history in 3c. C.E. on the lower Danube and later invaded the Roman Empire and were converted to Arian Christianity. Used in sense of "rude or uncivilized person; savage despoiler" (1660s) in reference to their fifth-century sacking of Roman cities (compare vandal, and French gothique, still with a sense of "barbarous, rude, cruel"). In 19c., in reference to living persons, it meant "a Gothicist" (1812), that is, "an admirer of the Gothic style, especially in architecture." Modern use as an adjective in reference to a subculture style (typically with lower-case g-) is from 1986, short for Gothic in this sense.
By 1982, when the legendary Batcave club opened in London, the music press had begun to use the term gothic rock to describe the music and fandom around which a new postpunk subculture was forming. [Lauren M.E. Goodlad & Michael Bibby, "Goth: Undead Subculture," 2007]