daybed vs futon

daybed

noun
  • A couch that can be used as a sofa by day and a bed by night. 

  • A long chair for reclining. 

futon

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

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

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

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