change tack vs repurpose

change tack

verb
  • To take a different approach. 

  • To change course or heading. 

repurpose

verb
  • To alter to make more suited for a different purpose. 

  • To reuse for a different purpose, on a long-term basis, without alteration. 

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