My husband's last name is Antoni. His father emigrated (was displaced) after WWII. The family was driven out of their home in Glaserhau, now called Sklene, in what is Slovakia. They insist they are not Polish either but Slovak. When they visited Slovakia in the early 1990s, my husband and his parents heard from the man at the border that Antoni was a "real Slovakisch name." They were probably originally Germans who moved to the area sometime around 1700. After the war, all German descendants living in the area were forced out. For us, anyway, that means they definitely were not Polish. My husband's father spoke German but did know some of the Slovak language.
A little background on my husband's family: His grandfather Josef Antoni was born in 1868 in Glaserhau; he died about 1936. His grandmother was Josef's second wife, Anastasia (called Anna) Weis Antoni, born, we believe, in the late 1880s probably. She died about 1938. Please contact me if you'd like to discuss further.