When the word brothel was first used in the English language in a 1393 poem, it was a noun meaning "scoundrel" or "wretch". Around a hundred years later, it came to be used in reference to unsavory women more than men and took on a definition of "harlot" or "prostitute". This spawned the phrase brothel-house, which was a place where prostitutes gathered, and the house was eventually dropped, giving us our modern form of the word. Going back, brothel comes from the Old English word breoðan, which meant "deteriorate" (implying that scoundrels were deteriorated and worthless humans) and further derives from Proto-Germanic breutan, "to break" (and an etymon of brittle). Finally, that's from Proto-Indo-European bhreu, meaning "cut". Usage of the word brothel in literature over time has been trending upwards, peaking in 2004.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.