plonk oneself vs slouch

plonk oneself

slouch

verb
  • To hang or droop; to adopt a limp posture 

  • To walk in a clumsy, lazy manner. 

  • To cause to hang down or droop; to depress. 

noun
  • Any depression or hanging down, as of a hat brim. 

  • Someone who is slow to act. 

  • A hanging down of the head; a drooping posture; a limp appearance 

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