customer vs interlocutor

customer

noun
  • A person, especially one engaging in some sort of interaction with others. 

  • A native official who exacted customs duties. 

  • A patron, a client; one who purchases or receives a product or service from a business or merchant, or intends to do so. 

interlocutor

noun
  • A person who takes part in dialogue or conversation. 

  • A man in the middle of the line in a minstrel show who questions the end men and acts as leader. 

  • A decree of a court. 

  • An interlocutory judgement or sentence. 

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