outwork vs vallation

outwork

noun
  • Agricultural work done outdoors in the fields. 

  • A minor, subsidiary fortification built beyond the main limits of fortification. 

verb
  • To work out to a finish; to complete. 

  • To work faster or harder than. 

vallation

noun
  • A rampart or entrenchment. 

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