blackthorn vs shillelagh

blackthorn

noun
  • A stick or staff taken from this tree. 

  • A large shrub or small tree, Prunus spinosa, that is native to Europe, western Asia, and north Africa. It has a dark bark and bears thorns. 

shillelagh

noun
  • A wooden (traditionally blackthorn (sloe) wood) club ending with a large knob. 

  • Any cudgel, whether or not of Irish origin. 

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