arbor vs rotunda

arbor

noun
  • An axis or shaft supporting a rotating part on a lathe. 

  • A shady sitting place or pergola usually in a park or garden, surrounded by climbing shrubs, vines or other vegetation. 

  • A grove of trees. 

  • A spindle of a wheel. 

  • A bar for supporting cutting tools. 

rotunda

noun
  • A round building, usually small, often with a dome. 

  • A Gothic typeface used in early printed books in Northern Italy, based on a rounded script developed in the 13th cent.; the manuscript hand on which this typeface was based. 

  • A roundabout; a road junction at which traffic streams circularly around a central island. 

  • A form of cupola that has pentagons rather than squares or rectangles. 

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