loiter vs mill around

loiter

verb
  • To remain at a certain place instead of moving on. 

  • To stand about without any aim or purpose; to stand about idly. 

  • For an aircraft to remain in the air near a target. 

noun
  • A standing or strolling about without any aim or purpose. 

mill around

verb
  • To move or circulate in a confused or disorderly manner within a limited area. 

How often have the words loiter and mill around occurred in a corpus of books? (source: Google Ngram Viewer )