Beyond lateral thinking to the orthogonal
In Laurie King's The Beekeeper's Apprentice, an informant relays a message to Sherlock Holmes that says "There's Glasgow Rangers with buckets of bees, and the toss is somebody's trouble." I'd read about Cockney rhyming slang in an abstract way before, as lists of examples, but seeing actual usage was striking. The passage is memorably peculiar yet impenetrably opaque, it's both a code and the mnemonics for the code. Recalling xkcd's comic on Password Strength, rhyming slang can work as a way to make up cryptic codenames and passwords. Of course, stay away from the historical slang terms like "trouble and strife" for "wife," but for target word C, make up a conceptually linked word pair A, B, where B rhymes with C. Ideally, the link between A and B intuitively makes sense to you, but isn't otherwise widely well-known. So A -> [B ->] C, where outsiders can't figure out the blackbox operation.