True! I meant the usual name now. For me it's the same as Engineer Manager: it seems to have come out of nowhere but it's the standard now. Before we called them simply "managers" (or sometimes "team leaders" of the non-technical variety).
PS: are you by any chance the same Izkata as the one in scifi.se?
I've been hearing it for about 5-7 years now, usually in the context of career paths. I think it became popular when companies realized that non all developers are made for management and you need a separate career track for people who want to advance, but don't want to be a manager.
Principal engineer, architect, etc all fall into the IC career path, while, manager, director, VP of eng, etc all fall into the management track.
It's more project management than people management. You likely have to lead projects and maybe a team, but you're usually not responsible for anyone's career growth (other than your own).
I also never saw this until pretty recently. At first I assumed people were talking about independent contractors because it was the first thing that came to mind, it possibly fit the context I saw the term used in and nobody explained the acronym they just dropped it there like I was supposed to know what it meant.
Took a bit longer to realize they meant individual contributor.
I dunno if it's just me, but it seems like the term came out of nowhere just a couple years ago.