picket fence vs rampart

picket fence

noun
  • A simple fence made from wooden pickets, connected by horizontal bars. 

  • A series of spaced perpendicular striations that occasionally occur in aurorae. 

rampart

noun
  • A defensive structure; a protective barrier; a bulwark. 

  • A defensive mound of earth or a wall with a broad top and usually a stone parapet; a wall-like ridge of earth, stones or debris; an embankment for defensive purpose. 

  • That which defends against intrusion from outside; a protection. 

  • A steep bank of a river or gorge. 

verb
  • To defend with a rampart; fortify or surround with a rampart. 

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