(EN) Antonio Sciarretta, Indo-European Roots, su digilander.libero.it/toponomastica/. URL consultato il 18 aprile 2020 (archiviato il 3 marzo 2016).
«*kel- 'spotted'
* Reconstructed from Sanskrit kalanka 'spot', kalka 'mud, smut', Greek kelainos 'black', Middle High german hilwe 'fine fog'
Variant: *kal- (or *kwal- ?)
Reconstructed from Greek kelis, -idos 'spot', Latin caligo 'fog', Old Irish caile 'spot', Old Church Slavonic kaly 'dirt'[...]
* Suffixed form *kalor in Calor fl. (Hirpinia)»