I would tend to think that it was nomenclature by Western Electric, like "D,F,G,H,J or L" station wire, "D" inside wiring cable or "F" cross-connect wire.
I do know that in the 1950's and 1960's, there was "JKT" wire, which I believe was quad but 20 gauge unlike today's 22 gauge. It was the stuff about the size of coax (RG59) cable and had paper between the jacket and the conductors. The paper never came off without a fight.
People look at me like I am crazy when I mention "JK" wire these days, despite the fact that there are millions of miles of it carrying DSL and dial-up Internet connections. Of course, it's now been deemed to be the bad stuff even after fifty years.
So, what is the answer? Am I close?
