Why use "Hell" to emphasize a statement?

I was watching Rocky last night and one of the lines got me thinking.

I was wondering why we use Hell in sentences like "A Hell of a lot better than…," "Hell, that's the best thing that's ever happened to me" and "Hell, I don't know."

The first example was what got me thinking the most: "A Hell of a lot better than something." The contradiction between Hell and better was what seemed a bit confusing to me.

Hell as an interjection is most likely short for bloody hell. The use of bloody to add emphasis to an expression is of uncertain origin. Recent research suggests that is is thought to have a connection with the 'bloods'—aristocratic rowdies who were the late 17th and early 18th century equivalents of 21st century 'Chavs' and 'Pikies.'

After the mid 18th century, bloody used as a swear word was regarded as unprintable, probably from the erroneous belief that it implied a blasphemous reference to the blood of Christ, or that the word was an alteration of 'by Our Lady.'

A widespread caution to using the term bloody arose, particularly in the US, and this is most likely where the use of simply hell came about.

A hell of (or one hell of) is used as emphasis for something very bad or great. The expression is used both in American and British English.

It cost us a hell of a lot of money.

Some expressions containing hell don't have a bad meaning. For example, for the hell of it means "just for fun," and hell for leather means "as fast as possible."