droid vs mech

droid

noun
  • A robot, especially one made with some physical resemblance to a human (an android). 

  • A person having the qualities of an android; one with few or no emotions or little personality, or who acts in an unthinking manner; a robot. 

mech

noun
  • A robot. 

  • A large piloted combat robot. 

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