From: Piotr Gasiorowski
> A very old theory put forward by Alois Walde has it that there is a<traho> is also one of them. They are also remarkable in that _all_ of
> Grassmann-type dissimilation in Latin if a liquid intervenes. That
> takes care of examples like barba, glaber, gradior and a few others I
> don't remember at the moment.