It has been 70 years since this song was first recorded.
The fragment of "Oh, Death" quoted here is close to the one sung by Sarah Gunning on her Folk Legacy 1965 album, "A Girl of Constant Sorrow."
The only line that differs is the last one, "I'll bring sexual death unto you from me."
I don't recall this line in any of the versions that I have; it either came from a recent rewrite or from the killer' himself.

The Doc Boggs version in the DT also is very similar.

Randolph, in "Ozark Folk Songs," has an extended version under the title "Conversation with Death," collected in 1941: vol. 4, no. 663, pp. 98-99. Randolph says: "A recent "Holy Roller" song, doubtless found in some of the printed songbooks." Its origin, however, has not been established (I haven't checked the threads for comments yet).

I don't understand your 'obscure' comment; anyone who is familiar with southern folk music knows it. It has been recorded several times since the first(?) recording in 1934.