scute vs tortoise shell

scute

noun
  • A horny, chitinous, or bony external plate or scale, as on the shell of a turtle or the skin of crocodiles. 

  • An old French gold coin. 

  • A proneural gene, often associated with achaete, that is required for the formation of many larval and adult sense organs 

tortoise shell

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

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