Noun: a rustling, especially of a woman's skirts (idea)

As surely as Pavlov's pet knew anticipation
I know

I have many such bells in my head
Associations that are countless:

Between perfume and a lover's touch
Chills across my shoulder blades when I see
A red dress float by a café window

This is why the French gave a word
To a single discrete sound
So subtle
And yet infinite

                                                                                                                         Frou frou

.

.

_{title from Merriamwebster.com}