set adrift vs slip off

set adrift

verb
  • To send a ship, boat or raft out to sea without a crew or resources to steer it. 

slip off

verb
  • To leave a port, anchorage or mooring 

  • To leave a place, or a meeting, without being noticed 

  • To remove an article of clothing 

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