By the same token, he said, nothing is more deadly than a person who is too enraged for expletives -- who cleanly and quietly picks up a gun and starts shooting.

Researchers have also examined how words attain the status of forbidden speech and how the evolution of coarse language affects the smoother sheets of civil discourse stacked above it. They have found that what counts as taboo language in a given culture is often a mirror into that culture's fears and fixations.

"In some cultures, swear words are drawn mainly from sex and bodily functions, whereas in others, they're drawn mainly from the domain of religion," Dr. Deutscher said.

In societies where the purity and honor of women is of paramount importance, he said, "it's not surprising that many swear words are variations on the 'son of a whore' theme or refer graphically to the genitalia of the person's mother or sisters."

The very concept of a swear word or an oath originates from the profound importance that ancient cultures placed on swearing by the name of a god or gods. In ancient Babylon, swearing by the name of a god was meant to give absolute certainty against lying, Dr. Deutscher said, "and people believed that swearing falsely by a god would bring the terrible wrath of that god upon them." A warning against any abuse of the sacred oath is reflected in the biblical commandment that one must not "take the Lord's name in vain," and even today courtroom witnesses swear on the Bible that they are telling the whole truth and nothing but.

Among Christians, the stricture against taking the Lord's name in vain extended to casual allusions to God's son or the son's corporeal sufferings -- no mention of the blood or the wounds or the body, and that goes for clever contractions, too. Nowadays, the phrase, "Oh, golly!" may be considered almost comically wholesome, but it was not always so. "Golly" is a compaction of "God's body" and, thus, was once a profanity.

Yet neither biblical commandment nor the most zealous Victorian censor can elide from the human mind its hand-wringing over the unruly human body, its chronic, embarrassing demands and its sad decay. Discomfort over body functions never sleeps, Dr. Burridge said, and the need for an ever-fresh selection of euphemisms about dirty subjects has long served as an impressive engine of linguistic invention.