barrier vs picket line

barrier

noun
  • An obstacle or impediment. 

  • A separation between two areas of the body where specialized cells allow the entry of certain substances but prevent the entry of others. 

  • A martial exercise of the 15th and 16th centuries. 

  • The lists in a tournament. 

  • A structure that bars passage. 

  • A node (in government and binding theory) said to intervene between other nodes A and B if it is a potential governor for B, c-commands B, and does not c-command A. 

  • A boundary or limit. 

verb
  • To block or obstruct with a barrier. 

picket line

noun
  • A barrier or fortification formed by pickets; a stockade. 

  • A boundary guarded by a picket (unit of soldiers). 

  • A boundary created by workers participating in a strike, generally at the workplace entrance, which other workers are asked not to pass. 

  • A line or rope held by one or many pickets, chiefly one used for tethering horses. 

How often have the words barrier and picket line occurred in a corpus of books? (source: Google Ngram Viewer )