mare's-tail vs witloof

mare's-tail

noun
  • especially, common mare's tail (Hippuris vulgaris) 

  • Erigeron canadensis (syn. Conyza canadensis), an annual weed 

  • Equisetum, a fern ally 

  • A long streaky cloud, spreading out like a horse's tail, and believed to indicate rain; a cirrus cloud. 

  • Any aquatic plant of the genus Hippuris, having narrow leaves in whorls. 

witloof

noun
  • Belgian endive, common chicory (Cichorium intybus) 

How often have the words mare's-tail and witloof occurred in a corpus of books? (source: Google Ngram Viewer )