cot vs futon

cot

noun
  • A simple bed, especially one for portable or temporary purposes. 

  • A cover or sheath; a fingerstall. 

  • A bed for infants or small children, with high, often slatted, often moveable sides. 

  • A wooden bed frame, slung by its corners from a beam, in which officers slept before the introduction of bunks. 

  • A pen, coop, or similar shelter for small domestic animals, such as sheep or pigeons. 

  • A small, crudely-formed boat. 

futon

noun
  • A thin mattress of tufted cotton or similar material, placed on a floor or on a raised, foldable frame as a bed. 

  • A round cushion used for Zen meditation, traditionally made of woven bulrush leaves. 

  • A specific kind of sofa-bed, with a fixed cushion that forms a mattress when folded down and a sofa when folded up. 

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