ubiquitin:
Why wouldnt a work of fiction be a legitimate source? A novel written in say Victorian england is a great source regarding how they spoke, lived dressed, and baked bread (if mentioned in the novel). Read Moby Dick (dont really it is long and incredibly boring), it is a great source of information on 19th century whaling and whaling towns.
Seriously? While there are indeed works of fiction that are historically accurate, there are many more that are not. Unless a work of fiction is actually known to be historically accurate, to attempt to prove history from it (without even noting that it is a work of fiction!), and then to use this so-called “proof” to assur a practice that is several hundred years old, is nothing short of ridiculous. I find it hard to believe any impartial and rational person could honestly believe the logic of that argument.
Tell me, should we assur beis din from sitting at a round table because King Arthur and his Knights did so in a storybook?
regarding your second paragraph:
“How was the shape of the cross made? Either with a bone of a pig or with a cross shaped key. There is no parallel to the Schlissel Challah here whatsoever.”
Really No parallel? “OR WITH A CROSS SHAPED KEY” No parallel at all
Of course not. One is discussing making a key shape, one is discussing use a key, among other things, as an instrument to make an entirely different shape. They have nothing to do with each other.
So once again, we do not have proof that this supposed pagan custom even existed, forget about placing it at the time and place where the Jewsih one originated.