Swearing achieves the same catharsis one gets from a hearty belch, an evening constitutional, or a good, long cry — it's a psychic purgative when one is suffering from emotional constipation. Because men are congenitally incapable of indulging in good, long cries, swearing provides them with a handy compromise when presented with the impractical alternatives of running away, crying, or fighting. Men can be hostile creatures, and swearing often allows them to exchange oaths instead of blows. As Mark Twain put it in Pudd'nhead Wilson, "When angry, count four; when very angry, swear."
—Richard Dooling, American writer and lawyer, Blue Streak, 1996