slide off vs slip away

slide off

verb
  • To leave a place, a meeting, etc., without being noticed; to slip away, slip off. 

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

slip away

verb
  • To leave a place, or a gathering, without being noticed. 

  • To die peacefully. 

  • To pass quickly, almost unnoticed. 

  • To disappear; to elude one; to recede; to dwindle. 

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