So I tracked down this programming manual for intercal https://3e8.org/pub/intercal.pdf and can't locate any mention to comefrom.

It is from a dialect called C-INTERCAL and is written with a space: 'COME FROM'

https://www.cs.virginia.edu/~asb/teaching/cs415-fall05/docs/...

It's also foundational in Threaded INTERCAL, where "multiple COME FROM statements with the same label cause the program to fork separate threads at each COME FROM":

https://esolangs.org/wiki/Threaded_INTERCAL

Thanks for that correction! I had memorized COME FROM as part of the original Intercal. My mistake.