Words, like children with attention deficit disorder, won’t sit still. The nature of language is change—relentless, unremitting, remorseless. Verbs are formed out of nouns like butterflies out of caterpillars (though some, like “incentivize,” seem more like butterflies turned into caterpillars). Neologisms, or newly coined words, abound. A great game, the language game, one that is played without a clock and knows no season. “The notion that anything is gained by fixing a language in a groove is cherished only by pedants,” wrote H.L. Mencken toward the close of the first volume of “The American Language.” Still, sometimes...