heffalump vs slummock

heffalump

noun
  • A clumsy or overweight person. 

  • (A child's name for) an elephant. 

  • Something that is elusive. 

slummock

noun
  • A slovenly person 

verb
  • To behave awkwardly or clumsily 

  • To behave lazily or indolently 

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