I dunno if it's just me, but it seems like the term came out of nowhere just a couple years ago.
PS: are you by any chance the same Izkata as the one in scifi.se?
Took a bit longer to realize they meant individual contributor.
Mine was "integrated circuit" which was like a really dystopian version of "human resources".
Principal engineer, architect, etc all fall into the IC career path, while, manager, director, VP of eng, etc all fall into the management track.
I often make this mistake because English is not my first language, and I confuse "engineer" with "engineering": in both cases it sounds to me "a manager who manages engineers", not "a manager who is an engineer him/herself". Kind of like a "Product Manager" is a manager who manages the product, not a manager who is a product!
From what I remember, it wasn’t intended as a long-term position, but was used in stop-gap circumstances (manager quits, tech lead temporarily takes on some people management duties) or for when an engineer was considering transitioning to the management track.
TLMs still have individual contributor responsibilities. M1s don't. The reason for that is generally that (especially junior) ICs aren't likely to push back against poor technical decisions knowing that the person they're pushing back against is also in charge of their rating. This feels quite fair based on my experience and as such I'm quite skeptical about TLMs in general.
Not true, TLMs can be D1+ level too at FB/Meta. Higher level TLMs more often than not tend to occur in more research-oriented organizations though (where the TLM is effectively a "principal investigator" type for some research area).
Strictly speaking, the roles of Engineer Manager and IC are incompatible; you cannot want to manage people and at the same time want to stay out of it. So in this particular context, "EM+IC" is a misnomer for "EMs who also need to be able handle tech/coding tasks themselves".