There's a "yella gals" song I used to sing that probably had "dou dou" or some variation thereof in the recording I learned it from; I couldn't figure out what the word was, and satisfied myself with "Tula", which I imagined as a woman's name - but I knew it wasn't quite right. It's the chantey that goes:

Once I was with Madam Colchis,
Up in Callao;
Hurrah, me yella gals,
[Tula] [Dou dou?] let me go.

Chorus
[Tula] [Dou dou?] let me go, me boys,
[Tula] [Dou dou?] let me go,
Hurrah, me yella gals,
[Tula] [Dou dou?] let me go.

Et cetera.

I don't know anything about the recording - it was on a tape someone handed me; sounded like a copy of a copy, and there was no identification on it. My impression is that the musicians were New Englanders.