blackthorn vs wolfberry

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. 

wolfberry

noun
  • The berry of this plant. 

  • Any of flowering species of the genus Lycium. 

  • Lycium barbarum or Lycium chinense 

  • The western snowberry, Symphoricarpos occidentalis, a shrub native to nothern and central North America. 

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