No problem. My message shouldn't have implied I was thinking of putting Daividh in the English category. When I referred to Celtic variants I had other names in mind, variants which may have in fact developed outside of the Celtic area.
As long as I have your attention I might as well list some specific names you may be able to help with. Many of the definitions are suspicious as well. Some of these are definitely Scottish or Irish surnames, but I don't know if they're Scottish/Irish given names.