Don't forget Intuition!!
Depending on your point view. Kickstart was the OS title, as that has to loaded first on the a1000, certainly in the circles where the first amiga's were seen in the UK at least, you would boot kickstart and load workbench. (edit: Akin if you would to: Booting DOS and Running Windows or Booting CP/M and running GEM), And when I first flipped from 64 to 500 I found it very frustrating that the CLI wasn't immediately available until you loaded a bastardised workbench disk.
So the name really depends on where you starting in computing. Workbench for me was just a fancy interface, i.e software, the CLI and writing in the shell was the OS of me
