golden root vs lignum rhodium

golden root

lignum rhodium

noun
  • Rhodiola rosea (Crassulaceae). 

  • An oil yielded by such plants, used in herbal medicine. 

  • The fragrant wood of several shrubs and trees, especially of species Convolvulus scoparius and Convolvulus floridus (Convolvulaceae) from the Canary Islands, and of the West Indian Amyris balsamifera (Rutaceae). 

How often have the words golden root and lignum rhodium occurred in a corpus of books? (source: Google Ngram Viewer )