Predestined to early death. When a person suddenly changes his wonted manner of life, as when a miser becomes liberal, or a churl good-humoured, he is said in Scotch to be fey, and near the point of death.
“She must be fey (said Triptolemus), and in that case has not long to live.” —Sir W. Scott: The Pirate, chap.v.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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