the walls have ears

Someone might be eavesdropping. Let's talk in my office—out here, the walls have ears.

Prov. Someone may be listening. (A warning that you think your conversation is being overheard.) Jill: Did I tell you what I found out about Fred? He—Jane: Shhh! Walls have ears. Don't say anything about our business dealings in here. Walls have ears.

The conversation is easily overheard, someone is listening, as in Be careful what you say; the walls have ears. This saying may come from a story about Dionysius of Syracuse (430-367 b.c.), who had an ear-shaped cave cut and connected between the rooms of his palace so that he could hear what was being said from another room. Similar listening posts were installed in other palaces over the centuries, including the Louvre in Paris. In English the phrase was first recorded in its present form in 1620.

You say walls have ears in order to warn someone that they should be careful about what they are saying because people might be listening. Take care and watch what you say. The walls have ears.

Your secret will be overheard. This warning allegedly refers to a story about Dionysius, the Greek tyrant of Syracuse (430–367 b.c.). He had an ear-shaped cave cut into a rock and so connected between palace rooms that he could hear what his prisoners said from another room. In the course of history, other palaces, including the Louvre in Paris and Hastings Castle in England, were said to have such listening posts. An early appearance of the term in print occurred in James Shirley’s play The Bird in a Cage (1633, 1.1): “Take heed what you say. Walls have ears.”