DEMETAE - DOBUNNI - DUMNONII = THE sunburnt man/tanned man ?

Hello

In Celtic we'got somes britain tribes called

Demetae

Dobunni

Dumonii

all living in S.O England (Walls/Cornouailles)

Can name's tribe come from same root

IE Dhem/Dhum- = DARK/SMOKE

Old irish Deim 
Old English Dimm/English Dim .
connecting with IE Dhub(n) = BLACK/GLOOMY

regarding to climate = Fog/smoke/mist ?

or regarding to an etnic specificity distinction ?

i remember the words of Tacite from Agricola speaking about Silures Tribe (neighbours form Demetae/Dobunni and Dumnonii) :

the swarthy faces of the Silures, the curly quality, in general, of their hair, and the position of Spain opposite their shores, attest the passage of Iberians in old days and the occupation by them of these districts; ..." (Tacitus Annales Xi.ii)

Pat
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