There is some code history here
They make reference to a lot of PDF copies of old documents.
This is the earliest one and it is interesting because it has a lot of opinions on grounding. One opinion is that the transformer feeding your house should be center taped and the center be grounded. This way there is only half of line voltage to ground anywhere you might get a shock.
The main reason given for grounding was protection against high voltages from a pole transformer primary to secondary short.
This 1904 code requires all wires to be fused.
It has a discussion about the pro and con of grounding on Page 53 and says
Inspection departments having jurisdiction may require grounding
and in the Appendix starting on page 123 is a section on ground detectors (A light bulb from each wire to ground) (Two per circuit) to show if there is a ground so you can find it and get rid of it.
Here is some 1918 info on grounding
I have two books written in 1919 and 1920 on house wiring and neither mentions grounding or a neutral or a return. The directions for a switch do not say which of the two conductors to wire it into, just pick one.
I have a permanent light plant (Generator) made by Kohler in 1947 It has two outputs, L1 and L2 neither are labeled ground L2 is connected to the negative battery terminal but neither side of the starting battery is grounded. (More info here.)
It appears that there was a period of time when neutral, Ground, fuseing, and other things were changing fast and some were not paying attention to the code.