amaranthus vs lamb's quarters

amaranthus

noun
  • Any of the genus Amaranthus; an amaranth. 

lamb's quarters

noun
  • Any of several similar plants of genera Chenopodium and Atriplex. 

  • Chenopodium album, of the goosefoot family, sometimes used as a potherb 

How often have the words amaranthus and lamb's quarters occurred in a corpus of books? (source: Google Ngram Viewer )