auctioneer vs sales clerk

auctioneer

noun
  • A person who conducts an auction on behalf of a vendor, taking bids to find the best price for the vendor. 

verb
  • To sell at an auction; to auction. 

sales clerk

noun
  • A person employed by a store to sell merchandise, assist customers in finding merchandise, and accept payment. 

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