ceil vs chalkboard

ceil

verb
  • To line or finish (a surface, such as a wall), with plaster, stucco, thin boards, or similar. 

  • To set a higher bound. 

noun
  • A ceiling. 

chalkboard

verb
  • To write or draw on a chalkboard. 

noun
  • A slate or enamel board for writing on with chalk; a predecessor to a whiteboard. 

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