This is an excerpt from Alfred, Lord Tennyson's The Idylls of the King.
A couple of notes on pronunciation: I had heard from an early age that in the case of Tennyson's long masterwork on Arthurian themes, the word "Idylls" was to be pronounced as if it rhymed with the family that the Reverend Dodson knew in Oxford, the Liddells. And so I carefully became habited to call it. But then I read somewhere (I don't recall where, I won't search for it today) that Hallam said his father pronounced it in the same way as what a car does at a stop light in the United States--i.e., as "idles".
Gawain can be pronounced with the stress on the second syllable, as is most common: "GaWAIN" with the first syllable sounding schwa, OR with the stress on the first syllable, as I did here. Given the place on the line--and that Tennyson was too skilled to not have been able to compose the line elsehow to fit the meter--I expect that, here at least, Gawain was stressed on the first syllable.
Tennyson has fallen from favor. In part rightly so, in part not. As Ezra Pound said, referring to early in his re-working of the poetic diction of English in the 20th Century, "To break the pentameter, that was the first heave". But as a result, we fail now to hear what readers a century and a half ago heard. There is much beauty in much of Tennyson's work. But there is much tedious rumpty-tum, too. Tennyson was the towering figure of the Victorian pentameter that Pound needed to break in Modern poetry. Of all poets, Tennyson was probably, apart from the flocks of bad late Victorian and Edwardian poets that thought they had the aesthetic well in hand, the poet most antithetical to what Pound saw as needing to be done to create a new, Modern, poetry.
In Tennyson's further defense, The Idylls of the King was a long narrative work, and he made it cohere. It was no mean feat, and it is deserving of our 21st-Century attention. [And I had another reason to turn my attention this way recently; an interesting currency to Tennyson in American Modernism that I will discuss elsewhere.] :-)
A "carcanet" is a necklace or jeweled collar. "Fool" means the court jester.