What's In A Mouth? Poem by Douglas Scotney

Is there something about a mouth in France
that stops a town's name from ending in bouche?

There's nothing stopping a mouth in Britain:
Bourne, Avon, Teign and Eye testify;
so do Ex, Fal, Yar and Lossie;
and Ports, Wey, Dart and Ply.

In France all I can see
is Port-de-Bouc;
but bouc is goat and goatee,
either or both, presumably,
fecund at the mouth of the Rhone.

Is it its teeth or its tongue:
is what's in its mouth
the reason why?
Is it what goes into it why,
why there's no Quoi-quebouche? *

Is it its sigh:
is what comes out of it why?