adarme vs piece of eight

adarme

noun
  • Synonym of peso, during periods when it was a Spanish coin notionally equivalent to an adarme of gold. 

  • A traditional Spanish unit of mass, equivalent to about 1.8 g. 

piece of eight

noun
  • The peso, a silver coin that was minted in Spain and its colonies from the end of 15th century, equal to eight reales (hence the name). 

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