perpetuate vs sustain

perpetuate

verb
  • To make (something) perpetual; to make (something) continue for an indefinite time; also, to preserve (something) from extinction or oblivion. 

  • To prolong the existence of (something) by repetition; to reinforce. 

  • To record (the testimony of a witness) which may be lost before a matter comes to trial. 

adj
  • Perpetual, or made perpetual; continued for an indefinite time. 

sustain

verb
  • To maintain, or keep in existence. 

  • To provide for or nourish. 

  • To encourage or sanction (something). 

  • To allow, accept, or admit (e.g. an objection or motion) as valid. 

  • To keep from falling; to bear; to uphold; to support. 

  • To confirm, prove, or corroborate; to uphold. 

  • To aid, comfort, or relieve; to vindicate. 

  • To experience or suffer (an injury, etc.). 

noun
  • A mechanism which can be used to hold a note, as the right pedal on a piano. 

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