mark off vs set apart

mark off

verb
  • To indicate as dealt with, as on a list. 

  • To separate by or as with a boundary line. 

set apart

verb
  • To distinguish, make obvious the distinction between (two things) or of (something). 

  • Used other than figuratively or idiomatically: to separate or isolate. 

  • To select (something or someone) for a specific purpose. 

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