dripstone vs walk-up

dripstone

noun
  • A protective moulding over a door or window that allows rain to drip away from the structure. 

  • Stalactites and stalagmites collectively. 

  • A water filter in which impurities are removed by running water through a porous stone. 

walk-up

noun
  • An apartment or block with stairs rather than an elevator. 

  • An informal visit to a control tower by a pilot, typically used as part of pilot training. 

  • An indoor or outdoor stand where food is sold to the public. 

  • A customer who arrives without a reservation; a walk-in. 

  • A mountain that can be climbed without specialist equipment. 

  • Colaptes auratus, northern flicker. 

adj
  • For which no appointment is necessary. 

  • Containing such flats. 

  • Reached by stairs rather than an elevator. 

How often have the words dripstone and walk-up occurred in a corpus of books? (source: Google Ngram Viewer )