To become or make more fretted; to cause worry or create a fretted pattern (archaic or rare usage).
Extended form of 'fret' with the suffix '-en', following Old English verbal patterns where '-en' intensified or made causative the base verb.
This word is barely used anymore, but it shows how English once loved adding '-en' to verbs—we still see it in words like 'darken' and 'lighten,' relics of a grammatical system our language mostly abandoned.
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