gradin vs staircase

gradin

noun
  • Any of a series of terraced steps or seats, as in an arena or an altar. 

staircase

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

  • A flight of stairs; a stairway. 

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

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 gradin and staircase occurred in a corpus of books? (source: Google Ngram Viewer )