polish vs tortoise shell

polish

noun
  • A substance used to polish. 

  • Refinement; cleanliness in performance or presentation. 

  • Cleanliness; smoothness, shininess. 

verb
  • To refine; to wear off the rudeness, coarseness, or rusticity of; to make elegant and polite. 

  • To apply shoe polish to shoes. 

  • To become smooth, as from friction; to receive a gloss; to take a smooth and glossy surface. 

  • To shine; to make a surface very smooth or shiny by rubbing, cleaning, or grinding. 

  • To refine; remove imperfections from. 

tortoise shell

noun
  • The shell of a tortoise, sometimes inaccurately the shell of a turtle, or that material. 

How often have the words polish and tortoise shell occurred in a corpus of books? (source: Google Ngram Viewer )