Kondrat

I think it's also Russian (archaic) and Ukrainian (archaic) Usages because last names like Kondratyev (Russian) and Kondratenko (Ukrainian) exist and it doesn't make much sense for them to be from the Polish name.

This is the historical spelling of this name in Poland, not used anymore. We use Konrad now in Poland. By the way, Kondrat is the last name of one of the best Polish actors, Marek Kondrat. [noted -ed]