OK: The Improbable Story of America's Greatest Word

It is said to be the most frequently spoken (or typed) word on the planet, more common than an infant's first word ma or the ever-present beverage Coke. It was even the first word spoken on the moon. It is "OK"—the most ubiquitous and invisible of American expressions, one used countless times every day. Yet few of us know the hidden history of OK—how it was coined, what it stood for, and the amazing extent of its influence.

Allan Metcalf, a renowned popular writer on language, here traces...