mantle vs tortoise shell

mantle

noun
  • Anything that covers or conceals something else; a cloak. 

  • A figurative garment representing authority or status, capable of affording protection. 

  • The layer between the Earth's core and crust. 

  • A penstock for a water wheel. 

  • A mantling. 

  • A gauzy fabric impregnated with metal nitrates, used in some kinds of gas and oil lamps and lanterns, which forms a rigid but fragile mesh of metal oxides when heated during initial use and then produces white light from the heat of the flame below it. (So called because it is hung above the lamp's flame like a mantel.) 

  • The back of a bird together with the folded wings. 

  • The zone of hot gases around a flame. 

  • The cerebral cortex. 

  • The outer wall and casing of a blast furnace, above the hearth. 

  • A piece of clothing somewhat like an open robe or cloak, especially that worn by Orthodox bishops. (Compare mantum.) 

  • The body wall of a mollusc, from which the shell is secreted. 

  • A fireplace shelf; Alternative spelling of mantel 

verb
  • To climb over or onto something. 

  • To become covered or concealed. 

  • To spread like a mantle (especially of blood in the face and cheeks when a person flushes). 

  • To cover or conceal (something); to cloak; to disguise. 

tortoise shell

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

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