Nineteenth-century American humor relied heavily on misspelling. As literacy became widespread, it was inevitable that skill in reading and writing would become markers of social class and background. Bad spellers in journalism and literature, usually rustics, provided a somewhat-better-educated middle class with amusement and a confirmation of their own superior status.

It is to this tradition that we owe the most substantial American contribution to the English language, the English word most universally understood and used: OK.

In OK: The Improbable Story of America’s Greatest Word (Oxford University Press, 210 pages, $18.95), Allan Metcalf, the executive secretary of the American Dialect Society, traces this universal word from its truly improbable beginnings to its current, equally improbable, status.

The origins of the word were documented half a century ago by the indefatigable Allen Walker Read of Columbia University. OK originated during a craze for abbreviations in Boston journalism, appearing for the first time ever in the March 23, 1839, edition of the Boston Morning Post as an abbreviation for all correct, understood as being spelled oll korrect.*

A couple of coincidences brought the fanciful abbreviation into common use. In the loony presidential campaign of 1840, Martin Van Buren’s partisans tried to counter William Henry Harrison’s popular appeal by referring to Van Buren as “Old Kinderhook,” from his family estate. Subsequently, Andrew Jackson’s political enemies, seeking to portray him as a backwoods illiterate, spread word that he initialed official documents with “O.K.,” for “oll korrect.”**

The word caught on, shedding over time its comic beginnings and becoming a widespread neutral affirmation.

So far, Professor Metcalf treads the ground pioneered by Professor Read, but he moves on to contemporary terrain, tracing its development in literature, business, and everyday speech. And its worldwide scope. OK—noun, verb, adjective, adverb, interjection—is understood by speakers of “Dutch, German, Swedish, Polish, Finnish, Italian, Spanish, Welsh, Hebrew, Korean, and Japanese, among many others ... with pronunciations adapted to their languages.”

It has become a useful, neutral term—indicating things that are not superior, not inferior, but just, you know, OK. Good enough. Serviceable.

It is, he suggests, a characteristically American term, representative of a pragmatic attitude toward life. And, extrapolating from the popularity of the transactional analysis catchphrase “I’m OK—you’re OK,” he argues that it represents a “two-letter American philosophy of tolerance, even admiration, for difference.” Bear with me; he has a point: “At the start of the 1960s in the United States, law and custom were quite different from what they are today. Discrimination against minorities and women was not only widely practiced but widely accepted. Today acceptance and even affirmation of differences have become pervasive, in law as well as in practice, and those values persist despite the encouragement to xenophobia caused by the threat of terrorism.” OK is “a mantra of tolerance and acceptance unprecedented in our history.”

I’m OK with that, and so should you be. Have a look at Professor Metcalf’s book yourself. It’s worth your time.

*There is a word, for which I am debt to Professor Metcalf, for bad spelling: cacography.

**There was not a shred of accuracy in the report, but it came to be widely believed, much as the “birther” nonsense has gained currency in our supposedly more sophisticated era.