couldn't-care-less vs perfunctory

couldn't-care-less

perfunctory

adj
  • Performed in a careless or indifferent manner as a thing of rote. 

  • Done only or merely to conform to a minimal standard or to fulfill a protocol or presumptive duty. 

How often have the words couldn't-care-less and perfunctory occurred in a corpus of books? (source: Google Ngram Viewer )