RE a name something like "Szarny tzetzl":
>> If it's "Czarny," that would be the Polish word for black in the German system of transliteration (Charny in the English system).
It makes a lot of sense that an heirloom tomato might have the word "Black" in its name.
These were the closest I found in Tatania's Tomatobase:
Kozula 126 Czarny Lagodny
Kozula 129 Czarny Twardy
This was in the description of both:
"The original cross was made by Anna Kozula, a well-known tomato breeder in Poland."
and
"F3 seeds were distributed to North American gardeners in 2010"
"Tzetzl" sounded Yiddish to me, so I looked that up. In Yiddish, "ZETZ" can mean a strong blow or punch or smack upside the head.
However, this is all speculative unless someone recognizes a known cultivar.