lucre vs petty cash

lucre

noun
  • Money, riches, or wealth, especially when seen as having a corrupting effect or causing greed, or obtained in an underhanded manner. 

petty cash

noun
  • Cash available for trivial purchases, especially limited funds for employees to use without close supervision. 

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