[Scoob]

Great info, Manji. So according to this info, from the Roman perspective, there was a continuum:

Romans (presumably: civilized/short/dark-haired) - Celts - Germans (wild/tall/blond)

I've also read translations of Roman accounts that said one Celtic woman could fight 3 Roman soldiers. This sounds like an exagerration, but the point is made: these barbarians were on average more robust than Romans.

19th Century British anthropologists and folklorists seem to have reiterated this continuum from the opposite perspective, when they described the Celtic-speaking peoples of the British isles (the Irish and Welsh more than the Scottish) as short and dark.