hoarder vs pack rat

hoarder

noun
  • One who hoards; one who accumulates, collects, and stores, especially one who does so to excess. 

pack rat

noun
  • One who collects or hoards, especially unnecessary things. 

  • Any of several small North American rodents, of the genus Neotoma, that have bushy tails. 

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