why do people swear? when do people swear?

Swearing per se is an unpleasant habit... but people has certain reasons valid enough to make them get excused from the commission of the act of swearing...

Sometimes, swearing is unintentionally commited because of the following reasons:

Extreme fear..... Extreme anger... Extreme reactions to unexpected startling incidents like a sudden drop or fall or more so, a startling appearance of an unexpected person coming in from nowhere....and many thousand reasons.