Well, if they have red hair they probably have Neandethal/Scots genes.
They were living on crannogs on the lake
European And Asian Genomes Have Traces Of Neanderthal
Migrating humans interbred with Neanderthals after leaving Africa.
Some Neanderthal lives on in the genomes of many modern humans. The genomes of most modern humans are 1–4% Neanderthal — a result of interbreeding with the close relatives that went extinct 30,000 years ago, according to work by an international group of researchers.
The 12 foot tall part could be an exaggeration or a change in how measurement is taken since the origin of the legend.
The giants in the legend might well have been Neanderthals, who scientists now say likely had red hair, and whose stocky build might have been described by an Indian word that was mistranslated into English as “giant.”