buck up vs pluck up

buck up

verb
  • To become encouraged, reinvigorated, or cheerful; to summon one's courage or spirits; to pluck up courage. 

  • To pass on to higher authority for resolution. See also pass the buck. 

  • To encourage; to hearten. 

intj
  • Cheer up; take courage; take heart. 

pluck up

verb
  • To summon positive emotion (especially courage); to muster. 

  • To remove or acquire by plucking from, for example, the ground; to pick up. 

  • To become more cheerful. 

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