archway vs staircase

archway

noun
  • A passageway covered by an arch, particularly one made of masonry. 

  • A doorway with a semilunar-shaped top. 

staircase

noun
  • A set of locks (enclosed sections of waterway) mounted one above the next. 

  • A flight of stairs; a stairway. 

  • A connected set of flights of stairs; a stairwell. 

verb
  • To modify (a signal, a graph, etc.) to reduce a smooth curve to a series of discrete steps. 

  • To increase one's share in a co-ownership. 

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