I used to call them "willies" when very young. Can't remember when my parents "persuaded" me to use wellies instead.
Pedagogs they were called I think. Mi owd school teacher used to always be on at me for turning up to school wi wet stocking feet.
as I now live in Wales I call them a Sex Aid TBH But I called them both Wellibobs and Wellies.... with an occasional Welligogs too.