Grey Wethers

In the Miss Marple short story The Thumb Mark of St. Peter, she mentions Grey Wethers as an example of how the context influences how a listener understands and interprets what is said.

Grey Wethers is a place in Dartmoor which has a stone circle. According to Miss Marple, if one were talking to a local farmer there and mentioned Grey Wethers, he was likely to conclude that one meant the stone circle. But it was equally possible that one was making a remark about the atmosphere. In the same way, an outsider hearing a fragment of the conversation, might think one meant the weather, when one might have wanted to refer to the stone circle. Thus when a witness repeated what was heard of a conversation, the witness would sometimes not repeat the actual words but would rather have rendered the speech into some other words which made sense in the context.

Miss Marple used this principle in solving the mystery of a "pile of carp"--the phrase which the parlourmaid and the cook had heard the dying Geoffrey Denman say. As domestic staff, they naturally interpreted what they heard in the context of their household concerns such as food and drink so it was natural that they heard "a pile of carp" when he actually meant "pilocarpine".