When:
Lookups on Merriam-Webster started spiking on June 29, 2010.
Why:
As the hearings began for Supreme Court nominee Elena Kagan, many media reports included Kagan's own thoughts on the process, revealed in a book review she wrote in 1995:
"Subsequent hearings have presented to the public a vapid and hollow charade, in which repetition of platitudes has replaced discussion of viewpoints and personal anecdotes have supplanted legal analysis."
Vapid means "lacking liveliness, tang, briskness, or force: flat or dull."
It comes from a Latin word meaning "flat-tasting."
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Merriam-Webster unabridged