sag off vs skive off

sag off

verb
  • To skive; to fail to attend school when required to do so. 

  • Used other than figuratively or idiomatically: see sag, off. 

  • To back off from an opponent against whom one is defending. 

  • To move too far leeward when sailing on the wind. 

  • To fall in share price. 

skive off

verb
  • To skive; to play truant; to slack off. 

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