operant vs peeper

operant

noun
  • An operative person or thing. 

  • Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment. 

adj
  • That operates to produce an effect. 

peeper

noun
  • Someone who peeps; a spy. 

  • The eye. 

  • An animal, such as some frogs, having a shrill, high-pitched call. 

  • A chicken just breaking the shell; a young bird. 

  • A peeping tom. 

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