Needs to have a meaning. Doesn't need to rhyme, you can freestyle.
Go back to the text and re-read a passage where Watson made a discovery. If Sherlock praises him, you've got your answer. I'm sorry if this wasn't much help, but I don't have any text to go off of.
its broadest sense, is a rhetorical device, literary technique, or event in which what appears, on the surface, to be the case, differs radically from what is actually the case.
