Swearing originally meant making an oath, and this usage is still used today in official and legal contexts. A court witness will have to swear to tell the truth etc. Very often this swearing is by God, or things considered holy.

Use of this type of swearing in inappropriate or trivial circumstances ("taking The Name in vain") was considered wrong and sinful. The use of the term swearing in common speech came to represent this usage. Many current "swear" words originate from this usage:

By my lady (the Virgin Mary) that was a good meal

became

That was B'lady a good meal

and eventually

That was a bloody good meal

Similarly

God Blind me, that was nothing to do with me

became

Cor blimey, that was nothing to do with me

See also

• Profanity