Serious history amongst these words. I don’t know why remember this term earlier than from a 1974 Bell Laboratories text by Brian Kernighan, Programming in C: A Tutorial. I read this one 1982. I remember my first hand on of “small c” back in late 1977, it was passed onto to me by an engineer who was out here conducting courses using the Scientific Ohio and later the Northstar Horizon.
It is funny how these things coming back to you as you get older. My memory is that it originated on a VAX / PDP bridging experiment back in the late sixties. Like most things that are old, the lore tends to rule the internet more than the fact.