Korczak is Polish for a wineglass, but I imagine the surname predates the use of glass for drinking vessels. An etymological dictonary might be useful here. There is a place in Ukraine called Korchak (near Zhitomir), but a surname from that should be Korczacki. Also the word korshak is Ukrainian for eagle. What I'm sure is relevant is that Korczak is a Polish "herb" name, but I don't want to tie myself in knots trying to explain what a "herb" is. I'll just say it's not botanical.