Thank you so much. It definitely is "Kasis", meanwhile. I double checked multiple records. Also, to anyone else, immigrants did not change their names at Ellis Island or wherever. They gave names (true or false) at the ports of emigration:
None of this even matters, though, because immigration officers at Ellis Island never wrote down immigrants' names.
Without gloating, then, I have to say that I was right about Great-Great-Granddad Julian Czerniecki (z"l). By the way, Dara Horn is actually very educated. In fact, her biography on her own page begins:
Dara Horn was born in New Jersey in 1977 and received her Ph.D. in comparative literature from Harvard University in 2006, studying Hebrew and Yiddish.
This is from the Amazon version. My anti-virus software blocked her website.