Christmas berry vs wolfberry

Christmas berry

noun
  • Synonym of toyon (“plant or its berry”) (Photinia arbutifolia, syn. Heteromeles arbutifolia) 

  • Synonym of spiceberry (“plant or its berry”) 

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 Christmas berry and wolfberry occurred in a corpus of books? (source: Google Ngram Viewer )