sag off vs wag

sag off

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

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

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

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

  • To fall in share price. 

wag

verb
  • To swing from side to side, such as of an animal's tail, or someone's head, to express disagreement or disbelief. 

  • To play truant from school. 

noun
  • A witty person. 

  • An oscillating movement. 

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