A knocking shop is a brothel, a house where sex is sold. The phrase is chiefly British, Australian and New Zealand slang, and it is almost always used with a knowing, slightly comic edge rather than as a neutral or clinical term. It turns up in casual conversation and in fiction as a euphemistic way of naming the place without spelling out what happens there, and it can also be used loosely as an insult, applied to any place regarded as disreputable or sleazy.
What’s the origin of the phrase ‘knocking shop’?
The phrase builds on an older use of the verb “knock” to mean to have sex, a sense recorded from the 1590s. “Shop” here works as it does in other slang compounds, treating the brothel as a place of business, somewhere a particular trade is carried on. Put the two together and the meaning is transparent once you know the older sense of “knock”: a shop for knocking.
The compound “knocking-shop” itself is dated to 1860 as slang for a brothel, growing directly out of that earlier sexual sense of the verb. From there it settled into ordinary use as one of the standard informal terms for a brothel across Britain, Australia and New Zealand.
By the mid-twentieth century the word had made its way into serious literary fiction. Evelyn Waugh used it in Brideshead Revisited in 1945, having a character describe an expensive establishment by saying it “always reminds me of one of the costlier knocking-shops… ‘Maison Japonaise’.” That the term could be dropped into a novel of that period, applied to a lavish rather than seedy establishment, shows how comfortably it had already settled into everyday British speech, useful precisely because it sounds jaunty rather than clinical.
A shortened variant, “knock-shop,” is also recorded, used as an alternative form of the same phrase. The full form has proved the more durable of the two, and modern dictionaries still enter it as current British usage, with the Cambridge Dictionary defining it plainly as a humorous term for a brothel. That humorous label fits the phrase’s whole history: it names something explicit while keeping the tone light, which is exactly what a good euphemism is supposed to do.