float someone's boat vs melt someone's butter

float someone's boat

verb
  • To interest or appeal to someone; to make someone happy. 

melt someone's butter

verb
  • To appeal to someone's fancy. 

  • To turn someone on; cause feelings of arousal. 

How often have the words float someone's boat and melt someone's butter occurred in a corpus of books? (source: Google Ngram Viewer )