The term Gothic comes from the Goths, one of the tribes that took part in the conquering of the Roman Empire. For centuries, the word stood for medieval barbarism, and sometimes was used to represent the culture of the Middle Ages generally: Gothic architecture, for instance.

Late in the eighteenth century, a new kind of novel made use of many of the traditional trappings of the Middle Ages: dark castles, secret passages, stormy nights, gloom, and terror. The early Gothic novels (Horace Walpole's Castle of Otranto, 1764, is often called the first) were actually set in the Middle Ages, although later examples of the genre (such as Mary Shelley's Frankenstein) were set in the present. The Gothic vogue probably peaked in the Romantic period with such authors as Shelley, Anne Radcliffe, and Charles Brockden Brown, but it survived well into the nineteenth century (as with Edgar Allan Poe), and, in spite of some transformations, into the twentieth.

From the Guide to Literary Terms by Jack Lynch.
Please send comments to Jack Lynch.
Note: This guide is still in the early stages of development.
Three question marks mean I have to write more on the subject. Bear with me.