One of the ongoing debates in Scottish and Irish onomastics is about the Kil- prefix. It is usually connected with Cill meaning a monastic cell, but may be a corruption of Coille (wood) and Gil (a gill or ghyll). Kilduff in Fife may be Coille Dubh (black/dark wood). There are also names in Scotland referring to oaks, sacred groves and so on.

Names like Cults outside Aberdeen may refer to forests. Calton Hill in Edinburgh appears to refer to hazel trees. Beith/Beath in placenames may refer to birch trees.

This is without going into the Brythonic names, of which there are many.