Slavic placenames

Amateur question regarding slavic root *lub or *lob meaning skull,
cranium (lubanja, lobanja) and from the same root also 'lubenica'
(watermellon).
The meaning can be even an exposed and visible hill.
So, placenames like Lubenik, Lubenice, Lubnica, Lubenka, Lubyanka,
and even Ljubljana and Ljubelj, I suspect, can be connected with this
root (locations with exposed and visible hill).
Placenames like Lomnica could also be result of development from
Lobnica and Lovnik from Lobnik.
Am I wrong?