Coded communication
Imagine a community of people who pass encrypted messages to one another, without knowing what they mean. Agent X has encrypted a message and handed it to messenger A, who passes it to messenger B, who passes it to agent Y, who has the codebook to decrypt the message. When A utters the message to B, she has no idea what it says; neither does B.
Intuitively, the meaning or content of A's utterance is the content of the decrypted message. That's why A and B don't know what the utterance means.