I've not heard the name before but if the earliest mentions are at Llandogo and near Monmouth, could its origins be from Skenfrith in Monmouthshire which is not far away, or from a now-extinct place Skenfield nearby? It reads like a locative surname to me (as does Skelcey which I still don't know the origin of). I have to say that locative surnames in Wales are almost unheard of, but east Monmouthshire may prove the exception, as usual.
Chris