Be wary, 'blarney' often implies the speaker's charm is insincere and possibly manipulative. His promise of unmatched riches was just blarney to get her investment.
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Cultural Origin
'Blarney' originates from an Irish castle; it's tied to legends of gaining persuasive speech. They said that kissing the Blarney Stone would endow me with the gift of blarney.
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Often Pejorative
Using 'blarney' can be seen as negative, especially if the context suggests dishonesty. The politician's promises were dismissed as mere blarney by the skeptical audience.