People’s looks are often mentioned with slavery, though. For example, while Julius Caesar abducted about a million Gauls, the blondest slaves in Roman markets were Angles.

Hollywood, at least in the HBO production “Rome” did get this part right. The main character has blonde hair, which is a political liability.

As noted in another comment, Zanj is the Arab word for black. Kafir is the word for nonbeliever and use more broadly. I’ve not heard it used racially.

The Atlantic slave trade and slavery in the US might have a word here

Was the Atlantic slave trade about race though? I don’t think that the tragedy that was the slave trade enslaved people because they were black, but because they were sub-Saharan Africans. I think it would have worked the same with any race that had been in those cultures.

There wasn’t a law or practice of enslaving people based on their skin color. As evidenced by the free blacks in other areas of the world that weren’t enslaved.

I think the racial stereotypes came about based on the race of the slaves, not the other way around.