"His physiognomy so grammatical!"

My edition is, I think, not really on the right track, when it converts "physiognomy" to "phraseology". Mrs. M is not talking about how Jack speaks, but how he looks. But Sheridan is so clever, he could very well have intended a double malapropism, and that could be one half of it, and the other would be a synonym of handsome or noble to describe Jack's face, which sounds like "grammatical"---I bet there is one that is a real hoot in its own right!