Origin
This proverb was first traced in 1952.
Explanation
Someone may be listening. (A warning that you think your conversation is being overheard.). Something you say to warn someone that it is not safe to speak at that particular time because other people might be listening. There is a risk of being heard, so pay attention to what you say. It is said that even the best kept of secrets can become known sooner or later. This is a warning to watch what you say, or what secrets you divulge, wherever you are, because someone might be listening.
Examples
Don’t say anything about our business dealings here. Walls have ears.
Why don’t we go and talk about this somewhere quieter? Walls have ears, you know.
Jill : Did I tell you what I found out about Fred? He…Jane: Shhh! Walls have ears.