This debate about the etymology of Britain interested me, and so I asked my dad, whose academic speciality is the history of our language/linguistics. He said your history through the Celtic word, Breukelen, is accepted among academic and scholarly circles as the correct etymology of that word.

The problem with the Hebrew word "brit" is that that's actually a Roman alphabet spelling of a word that's actually originally seen in the Hebrew alphabet, and so brit in our alphabet does indeed look and sound like part of "Britain," but in Hebrew the real spelling of that word looks completely different from the b-r-i-t and so it wouldn't have been converted into the Roman alphabet spelling early enough to correspond with the first use of that word in English/British history. The Celtic influence makes imminent sense, especially considering the geographic and linguistic influence of Celtic history on Great Britain. Professor Dad said, "Our language is one of the most infamous for appropriating words from other languages, but we've appropriated nearly all of them from Romance or Germanic languages with similar alphabets and phonemes." Hope that helps!