indirect vs source

indirect

noun
  • An indirect cost. 

  • An indirect radiator 

adj
  • Not of obvious or immediate cause, but as a secondary result 

  • Not focused straight at the target or subject, but by more subtle means 

  • Not involving the quickest, shortest, or most convenient path 

verb
  • To access by means of indirection; to dereference. 

source

noun
  • A reporter's informant. 

  • Source code. 

  • The name of one terminal of a field effect transistor (FET). 

  • Spring; fountainhead; wellhead; any collection of water on or under the surface of the ground in which a stream originates. 

  • The person, place, or thing from which something (information, goods, etc.) comes or is acquired. 

verb
  • To obtain or procure: used especially of a business resource. 

  • To find information about (a quotation)'s source (from which it comes): to find a citation for. 

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