DC vs District of Columbia

DC

verb
  • To become disconnected from a network. 

District of Columbia

name
  • The federal capital region of the United States of America. The City of Washington used to be a municipality within the District of Columbia until 1871, when two entities were merged. For this reason, the district is also generally known as Washington, D.C. 

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