futon vs mattress

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. 

mattress

noun
  • A pad on which a person can recline and sleep, usually having an inner section of coiled springs covered with foam or other cushioning material then enclosed with cloth fabric. 

  • A form of retaining wall used to support foundations or an embankment 

verb
  • To cover with a thick layer, like a mattress; to blanket. 

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