As with all these fun things, there are kernels of truth. Diablo does tend to drop Dol runes. "Trout" does have a root in Greek meaning "nibble" or "gnaw".
First, the hit points. Diablo in Normal Mode of Diablo 2 has 13818 hit points (according to the useful Diablo Wiki). So we can rule out that little piece of numerology.
Second, the error message. We need to see a screen shot of the error before we can really be confident. Otherwise, someone is just playing around with hex.
Third, the item. I’ve never encountered a "Gnaw Fold" ring in my play, and I can’t see a note of it in the item lists I’ve checked. Though I’m open to the idea, I don’t think it exists. The solution might be to install and not update, then play through single-player in an attempt to find it. . .maybe someone else has the time.
So, with no item, we can’t test the theory and get a screenshot. I call this a fun myth until someone can show me otherwise.
