achene vs pecan

achene

noun
  • A small, dry, indehiscent fruit, containing a single seed, as in the buttercup. 

pecan

noun
  • A smooth, thin-shelled, edible oval nut of this tree. 

  • A half of the edible portion of the inside of this nut. 

  • A deciduous tree, Carya illinoinensis, of the central and southern United States, having deeply furrowed bark, pinnately compound leaves, and edible nuts. 

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