NORN KJOKL

Well, Hnolt, while that may be true, it could also just be a trick used by skalds of the time. Kinda like Nightwish did in the song Amaranth:

"cAress the one..." (instead of the proper "carEss the one...")

The Shetlandic example you give screams English influence. "lavErnee" is "totally" how I'd expect an English speaker (or maybe a Scots speaker, since I have virtually no experiences with it) to mispronounce líverni.

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Ungur nemur, gamal fremur.
Gløgt er gestsins eyga.

Well, if stress was moved from short vowels in first syllables, then surely this vowel would first reduce and then disappear. I'm thinking about the Old Norse cognate to German genug: gnógr, which then later became nógr in all the daughter languages. (Unless Icelandic retains an archaic *gnógur).

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Ungur nemur, gamal fremur.
Gløgt er gestsins eyga.