An archaic or dialectal form meaning to flutter, flicker, or move in a restless, trembling way.
From the same Old Norse 'flitra' root as 'flitter,' with the -ern suffix sometimes added in dialectal or archaic English to create alternative verb forms, similar to how 'glitter' and 'glittern' existed.
English used to love adding -ern to verbs for no reason other than how they sounded! This is why we have weird words like 'glittern' and 'flittern'—linguists call this 'frequentative' forms, meaning they emphasize repetitive or continuous action.
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