History Memes

Many freedmen after the US Civil War also adopted new surnames to separate themselves from slavery, adopting common last names or last names of white folk they were exposed to during the liberation of the South - including ~150,000 Irish-Americans who served in the Union Army. Furthermore, while Irish were considered white before the US Civil War, they were also 'lower' in social status, and intermarriages between white Irish and free Black folk were more common than with the white Anglo-American majority.

This isn't to say "definitely not" for "Does a Black person with an Irish surname have a bad history behind that surname?" - there was a significant minority Irish-Americans amongst the slaver class in the US. But it's also much less certain than the meme implies.