Thomas W. Talley's 1922 collection "Negro Folk Rhymes" has a rhyme he calls "Wild Negro Bill" {p. 94 of Kennikat Press edition.

The verses Talley presents contain the N word {represented in my post as "N---"}

I'se wild N----- Bill
From Redpepper Hill.
I never did wo'k an' I never will

I's done killed de Boss.
I'se knocked down de hoss.
I'se eats up raw goose widout apple sauce!

I'se Run-a-way Bill,
I knows dwy mought kill;
But old Mosser hain't cotch me,
an' he never will!

---

Talley wrote that many of his songs were generations old..Since sneaking into railroad cars was often used by runaways, could
'Wild N--- Bill' be the source of "Railroad Bill?