flagpole vs keep back

flagpole

verb
  • Exit a country momentarily and reenter. Usually this is done to satisfy immigration requirements. 

noun
  • A tall pole up which one or more flags may be raised and flown. 

keep back

verb
  • To stay back; to refrain from approaching. 

  • To hold back; to refuse to give or share. 

  • To restrict or restrain. 

  • To prevent (a pupil) from advancing in a course. 

How often have the words flagpole and keep back occurred in a corpus of books? (source: Google Ngram Viewer )