Nobody has IC as a title, it’s a whole class of job families that don’t require/revolve around managing other employees. Data Scientist, Software Engineer, Data Center Technician are all ICs. It’s just a more positive way of saying “not people manager”, especially when you are trying to build a culture that going into people management shouldn’t be the only career path.

why do you need to say "not manager"? most people are in the nature of things not managers. and if you do need, for bad, bad reasons want to differentiate them, how about NMs? oh, but that would be to obvious for the current crop.