The word "Gothic" comes from the Goths, a tribe of former Germania who gave nearly as good as they got when it came to standing up to the Roman Empire. The Goths were considered wild and uncivilized, which isn't really fair considering that they left behind some pretty decent manuscripts proving that they had a sophisticated written language.
"Gothic" later became associated with a style of western European architecture, characterized by leaden glass windows, turrets, pointed spires, and flying buttresses. Later, Victorian Gothic brought this style back in a much cuter and more accessible manner. At the same time, the Gothic novel was created by the writer William Beckford, whose book "Vathek" came out in 1782.
This created a genre that has been popular ever since, from Ann Radcliffe's "The Mysteries of Udolpho" (all four volumes) to Kate Morton's "The Lake House." In between, there are books that influenced the genre, such as "Frankenstein" by Mary Shelley. Fast forward to the modern day and "Goth" has become its own fashion and lifestyle aesthetic.
Where do you fit into all this? We can tell you, right down to the proper name you should adopt for your Gothic alter ego - if you'll just tell us about the Gothic pile in which you intend to find your inner darkness. Let the hunt begin!