An interesting question raised in my mind by Morgan Llewellyn's Red Branch: what is the origin of the name Ulster?

She has a throwaway reference to the Ulaid being named for the wool they produced - this would link the word to modern Irish olann, which is a cousin of Welsh gwlan and goes all the way back to Proto-Indo-European *wlna and thus English woollen, and (dropping the initial w) Latin lana and French laine.

But not everyone believes this; the shift from the initial o of olann to u of Ulaid seems unpopular among linguists. Instead the received wisdom, including that of the great Pokorny, is that the ul of Ulaid is from Irish ulcha meaning "beard". This root supposedly comes from Proto-Indo-European *pul- which otherwise has only an obscure Greek cognate transcribed as pylinx and meaning hair on the posterior, and an Old Indian root pula meaning when your hairs standing on end.

Ptolemy calls the people of the northern part of Ireland the "Uoluntii", which doesn't help as it is evidence in both directions.

I was a bit dubious about the idea that Celtic words drop an original Indo-European “p”, but this turns out to be reasonably well attested – the root *palam turns into Latin palma and thus English “palm”, but Irish lamh; likewise father/pater/athair and first/primus/roimh. So I am convinced by that bit.

But for some reason I prefer the idea that the Ulaid were so-called because they were wool producers rather than because they had beards (which would I suppose make them equivalent to the Lombards). It seems more convincing to derive the toponym from economic activity than shaving fashions. (However, if there is no other case of an initial o shifting to u in Irish names, I shall have to concede to the beard theory.)