It doesn't have anything to do with ACDelco's "ETC" line. That is just a relabeled part they happen to distribute. Molex is maker as far as I know, instruction sheet attached.
Original patent attached.
I also haven't been able to find any history online, but based on patents ETC Inc was a company that designed/made crimp tools and electrical connectors at least as early as the 60s.
I found a patent that is shared with ITT, so I think they were part of that conglomerate at some point. It must have ceased to be an independent company long before the intern et.
Given I've only seen it in the wild on Molex-specific tools and they have no other presence I could find, I gather is now a wholly owned subsidiary/completely folded into Molex (Koch).
This confirms that theory, although wish it were better sourced:
https://www.encyclopedia.com/social...nd-labor/businesses-and-occupations/molex-inc
