True enough, re: the Mabinogion. In 'Cainc y Medelwr' it is certainly 'strain/air' and to translate it as 'branch' is ... OK - mildly misleading.    The Reaper's Strain/Air makes sense; The Reapers Branch doesn't.

But you are COMPLETELY correct to say that, if someone is using 'Branch', one needs to know about it, for googling purposes.

It strikes me that someone didn't ask a Welsh speaker for a translation, just went to a dictionary. Never a very good idea. I remember an alternative theatre company of some standing coming to a town near here for a week's residency. Acknowledging that it was an area with a high percentage of Welsh speakers, they had their marketing person (a Welsh learner) translate their leaflets. They had quite a good turn-out for the opening parade through the town. The locals were curious to see them 'process up the high street waving bright paving stones'.

(llechi = paving stones or, alternatively, FLAG stones. Get it?)

sian