Yesterday I read Kathleen's post in Fashion Incubator discussing the difference between tucks and pleats.
In the comments Marilyn mentionned that some "fashionisti" snobs used the french term "ruche" instead of gather or gathering.
To confirm her assertion here's a tutorial I found in my personnal library concerning "ruches". These are much more tan simple gathers.
Hopefully, this will be of some help or interest to somebody.
The french explanations may be somewhat confusing but the images speak for themselves.