Question about Mojito made w/dark rum and terminology

Some guy came in to FI asking for a Mojito made with dark rum, but he asked for it by asking for a Mojito Mulatto. He was completely taken aback that we didn't know the drink instantly by name. Anyone familiar with this drink name? He was from Georgia - maybe it's common in The South?

Additionally, I relayed this story to a Hispanic friend of mine and she gasped when I used the word Mulatto. I know the New Orleanian meaning of the word, because my grandpa, who was African-American, was from there: Mulatto is a term that has been used to delineate African American familial lines. I didn't realise that there are people who feel it has stigma attached to it. Anyone else have experience with this word?

Mahalo,
~T

I have heard of a drink called a Mulatto from Mexico. It is Kahlua, Tequila, and cream. My Mom used to drink them when she lived there. I've never heard of it in association with a Mojito...