Why was the term electromotive "force" used instead of voltage or potential difference in original Faraday's law?
Why is the term electromotive “force” was used instead of voltage or
  potential difference in original Faraday's law?


Volt Wiki: -


  In 1881, the International Electrical Congress, now the International
  Electrotechnical Commission (IEC), approved the volt as the unit for
  electromotive force.


Michael Faraday discovered electromagnetic induction in 1831.