Where does Tiddles come from?

"So we know about catty, but what about Tiddles?  Is it Anglo-Saxon?", writes a correspondent.  It is. 

The OED says "tiddle" - to fondle - comes from "tid", which means soft or nice. (Obiter, I wonder whether there might be a related female anatomical term, but anyway).  The OED credits this explanation to that 1755 best-seller, The Dictionary Of The English Language, by none other than the renowned brainbox and cleverest man in England, Dr. Samuel Johnson.

Talking of cats, by coincidence, Baldrick's suggested definition for "dog" in Dr Johnson's Dictionary was: "Not a cat".  

Does Dr Johnson's dictionary really not contain "aardvark"?