dumping ground vs tipping

dumping ground

noun
  • A landfill. 

  • Any place where unwanted items are sent. 

  • A presumably polyphyletic supraspecific taxon where species of unclear affinities are placed. 

tipping

noun
  • The dumping of rubbish. 

  • A distinct articulation given in playing quick notes on the flute, by striking the tongue against the roof of the mouth; double-tonguing. 

  • The act by which something is tipped or inclined. 

  • The practice of leaving a tip (gratuity). 

  • A competition where entrants aim to tip (predict) the outcomes of sporting events. 

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