E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
He was like an anatomyi.e. a mere skeleton, very thin, like one whose flesh had been anatomised or cut off. Shakespeare uses atomy as a synonym. Thus the hostess Quickly says to the Beadle: Thou atomy, thou ! and Doll Tearsheet caps the phrase with, Come, you thin thing; come, you rascal.2 Henry IV., v. 4.