dongle vs plug-in

dongle

noun
  • Any small device that plugs into an electronic device, typically a computer, and alters its functionality. Common examples include wireless modems, digital media players, software copy protect devices, and adapters. 

  • A hardware device utilized by a specific application for purposes of copy protection. 

plug-in

noun
  • A module or device that interacts with another to add a specific feature or function. 

  • An electric vehicle that can be recharged from an external power source. 

  • Anything that plugs into something. 

adj
  • Able to be extended with further components in a modular fashion. 

  • Designed to be plugged into an electrical power outlet or circuit. 

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