Glenn is correct. The name "stumpjumper" is in reference to lineman who climb wooden poles. Lineman would often refer to their selves as stumpjumpers, if an outsider used this term it would usually result in a fist fight.
I don't know the exact origin of "narrowback", my guess is it was in retaliation for inside wireman calling lineman stumpjumpers. The reference was probably to imply inside wireman did not have the physical attributes of the lineman.
This was usually all in fun, and not taken serious.
It does illustrate a separation of lineman and wireman, in the electrical trade.
This separation also created a different viewpoint for the same thing.
Lineman connecting distribution systems, refer to the grounding electrode conductor, neutral, equipment ground, and bonding jumper, as a (MGN) multi-ground neutral system.
Wireman, and the NEC, refer to the various conductors as individual systems. There is a change in definition at the secondary supply of the distribution transformer.
The completed product is the same, only the names change. I personally feel this has created a lot of confusion in understanding the technological reason for grounding, bonding, and providing low impedance path for fault current.
