My favorite Star Trek episode of all time is “Darmok,” in which Captain Picard and the Enterprise crew encounter an alien race that communicates entirely through metaphors and allegories. Near the end of the episode, Picard and the other ship’s captain end up exchanging stories from their home worlds in order to establish a way of describing their newfound friendship to each other.
Tell a story, in the style of a myth or a fable, that boils down to a specific message that could be communicated à la Tamarian linguistics. It could convey friendship or conflict, a command, or even a term of endearment. Make it clear enough to be guessed at through context, but vague enough to confuse people when you randomly throw it into a conversation. And then randomly throw it into a conversation, just for kicks.