Most of us work from the "Theory of Multiple Working Prejudices," which has served historians and investigators for centuries (although it is usually glorified by referring to hypotheses).
Seldom does the answer become clear-cut.
Both of us are working from our evidence-based prejudices, but the evidence is based on shaky ground. That is why discussions continue.

Bulgine
"People knew "bulgine" was a Black dialect term." I dispute that, it seems to have been in general slang use by firemen, sailors, and especially railroaders, who have kept the word current (it came into the music hall and literature from these usages).
It had its origin in the Bull engine, a steam engine for pumping water, invented in Britain, but much copied. The OED gives this as the source; "Bull + enjine, and define it as "a locomotive or steam engine."
The Oxford English Dictionary quotations show its rather sudden adoption as a slang term in the 1840s, and its use in a novel and the music hall.
As noted in several writings, sailors disliked steam pumps or steam hoists, which tended to fail when they were most needed. Some chantey singers (notes in their albums) label it a ships or dockside term for a steam engine, but they are not aware of railroad, fire or other uses. Early high-pressure engines (came into use in the 1840s-1850s) tended to have problems.
I can find no evidence that the word was originated by Blacks, its derivation from the Edward Bull engine is logical.