http://www.nytimes.com/2005/09/20/science/20curs.html?_r=1&pagewanted=all
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.