head restraint vs pillow

head restraint

noun
  • The headrest of a seat in a motor vehicle. 

pillow

noun
  • A soft cushion used to support the head in bed. 

  • A pillow lava. 

  • The socket of a pivot. 

  • A block under the inner end of a bowsprit. 

  • A kind of plain, coarse fustian. 

  • A piece of metal or wood, forming a support to equalize pressure; a brass; a pillow block. 

verb
  • To rest as on a pillow. 

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