A question for lexicographers

[Douglas G. Wilson]

Recently a correspondent asked me about the origin of the word "poontang".
I consulted the standard references, which mostly agreed with my first
impression that it is derived from French "putain".

OED, M-W, AHD, Cassell's slang dictionary, and many others cite only this
derivation (some with 'perhaps', 'probably', etc.).

My Random House dictionary expresses doubt on phonetic and semantic
grounds, and cites a possible origin in a minor language of Sierra Leone --
IMHO absurdly implausible in the absence of strong confirming data.

Partridge also demurs, and prefers an (apparently unspecified) Amerind
origin -- a priori very implausible IMHO ... as well as inchoate.

My question is this: Is the putative origin from French based only on a
plausibility argument (i.e., the sense is right, the phonetics is right,
the milieu is right [via Louisiana French or post WW I]), or is there some
actual evidence of the derivation (e.g., early attestations of transitional
forms, or memoirs from ca. 1920 stating that the word came from France or
New Orleans or wherever)?

I agree with the apparent majority view that the French derivation is
plausible on all three grounds. But I have developed at least one
alternative derivation which seems at least equally plausible, yet which
I've never seen explicitly presented anywhere: before I do further
'research', I'd like to know whether there is firm (or somewhat firm)
evidence for the derivation from "putain".

Can any of the lexicographers (or other scholars) help me?

-- Doug Wilson