all get-out

You may have heard or read any number of these expressions:

• DSL is faster than all get-out!
• I am hungry as all get-out!
• she is fun as all get-out.
• This is frustrating as all get-out.
• As original as all get-out
• Funny as all get-out
• Busy as all get-out
• Groovy as all get-out

But what does it mean? Well hearing it in context, it's pretty clear that is is meant to emphasise an adjective. This is sort of similar to words like "heck" (or "hell", or any of a number of other adjective-enhancers); you could, for example, say "DSL is faster than heck", for about the same effect. However, the reverse is not true - a phrase like "what the heck?" cannot be transmogrified to "what the all get-out?". This would just not make sense.

So, my friends, I am, quite frankly, mystified, as to what the phrase really means. Most people I have asked about it have never even heard the phrase, the ones who had, had no idea where it originated, or what it really means.

Can anyone help with the etymology?