I have started reviewing neuropsychology books and material to prepare for ABPP neuropsychology exam and in one of the books the name Sir William Osler is listed as the first physician to use the word Neuropsychology and D.O. Hebb was the first to use it in his 1949 book titled "The Organization of Behavior: A Neuropsychology Theory." Apparently, in the early development of neuropsychology, it was common for physicians/psychologist/researchers to steal others works and take credit. I believe Halstead was originally a comparative-experimental researcher/psychologist and most of the tests for the Halstead-Reitan Neuropsychology Battery were actually developed by others but they attempted to standardize procedures with norm referenced groups. From what I was informed by one of my supervisors, it was quite common for these historical figures in neuropsychology to have problems with alcoholism and drug addiction (Heroin/Opium/Cocaine) and we all know about Freud and how most of his theories were stolen and his Cocaine Addiction. Surprising, I too am having trouble finding most historical information about the history of neuropsychology but it is not a main area of focus on the ABPP exam from what my supervisor tells me. Apparently, one of Luria female associates he was involved in a long-term affair was responsible for stealing and selling much of his research to Americans and Europeans back during the Cold War when it was hard to communicate with Russians.
From what I can tell from my readings and discussion with supervisors, many of these historical figures were not overly concerned about following standardized ethical models and it is not exactly clear who actually is the founder of neuropsychology. I guess if you were to get technical we do not have clear evidence of early on research especially in the Eastern/Asian parts of the world.