Can you tell ethnicity by last name?

You can sometimes make an educated guess about ethnicity by last name, but you cannot determine ethnicity with certainty by last name alone, as last names travel, change, and are adopted across ethnic groups. Last names often have linguistic and geographic origins that correlate with ethnicity, for example Blanco means white in Spanish and is Hispanic ethnicity from Spain, common in Mexico and Spain, suggesting Spanish or Latino ethnicity. Chapman is English, meaning merchant, suggesting English ethnicity. Cohen is Jewish, specifically Kohanim priestly Jewish ethnicity. Singh is Punjabi Sikh Indian ethnicity. Kim is Korean. However, many factors make ethnicity by last name unreliable, including intermarriage where children take father's name but have mixed ethnicity, adoption where child takes adoptive family name, immigration where names are anglicized, slavery where enslaved people took owners' names, and name changes for personal reasons. In multicultural countries like USA, Canada, and UK, a person named Blanco could be Mexican, Puerto Rican, Filipino, or even non-Hispanic who married into family. A person named Chapman could be English, but also African American with English surname from history. So last name can suggest probable ethnic origin or linguistic origin, like Spanish, English, Jewish, but cannot definitively tell ethnicity, which is cultural identity and genetic ancestry. Use last name as clue, not proof, and ask person how they identify.