Everything about "pox leber" as a minced oath, and an earlier source.

[Bluetoes101]

"Pox liver! What is this place?"
I've come to look at that case of "pox leber" like "By Merlins beard!"  .. because its funny. But I think it's closer to "Goodness gracious!" Mauro. 

I actually think your example (dog in the grapes) may ring true with 116v, and what Katherine Hindley was saying might be the case in Koens video. Basically "if you know, you know". Earlier tonight I was reading about a charm to draw out 9 worms from a person into an arrow head using magic words, then a wizard(?) fires the arrow into the woods so the worm is returned home, as the woods in where the demons live, then the person will get better. 

If I were to note the words down, I can imagine something like

"Wizard worm arrow abracadabra
magical stuff + magical stuff + magical stuff + magical stuff
magical stuff + magical stuff + magical stuff + magical stuff
blah blah - so then fire the arrow."

Then there's us hundreds of years later trying to work out what "Wizard worm arrow" ???????? "so then fire the arrow" is all about  
Maybe they just knew "dog in the grapes".