cat's meat

Animals' lungs used to be sold as food for cats.

cat's meat (uncountable)

1. (UK, obsolete, slang) A person's lungs.
   • 1821, J. Burrowes, Life in St George's Fields:

     You must let him have all the jaw-work to himself, and give a holiday to your cat's meat.

• “Cat's-meat” in [John Camden Hotten], The Slang Dictionary […], 5th edition, London: Chatto and Windus, 1874, page 111.

• castmate, mactates