birch vs collar beam

birch

noun
  • A birch-bark canoe. 

  • A hard wood taken from the birch tree, typically used to make furniture. 

  • A stick, rod or bundle of twigs made from birch wood, used for punishment. 

  • Any of various trees of the genus Betula, native to countries in the Northern Hemisphere. 

verb
  • To punish with a stick, bundle of twigs, or rod made of birch wood. 

  • To punish as though one were using a stick, bundle of twigs, or rod made of birch wood. 

collar beam

noun
  • A horizontal piece of timber connecting and tying together two opposite rafters. 

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