When:
These words became top lookups on Merriam-Webster beginning July 19, 2010.
Why:
On July 18, former Alaska governor Sarah Palin tweeted a word that isn't in any dictionary:
Ground Zero Mosque supporters: doesn't it stab you in the heart, as it does ours throughout the heartland? Peaceful Muslims, pls refudiate
Gov. Palin's coinage attracted interest in the two words that seemed to have been blended into refudiate.
Refute and repudiate have related meanings, and sound alike. Refute means "to deny something by providing evidence that proves it is false or incorrect"; repudiate means "to reject something as untrue or unfair."
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Merriam-Webster unabridged