burgh vs metropolitan area

burgh

noun
  • a borough or chartered town (now only used as an official subdivision in Scotland). 

  • a small mound, often used in reference to tumuli (mostly restricted to place names). 

metropolitan area

noun
  • An area of population usually with a central or core city and surrounding towns or suburbs. 

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