A Black person. A reference to Africans, used as slave-labor, picking cotton on Southern United States plantations prior to the American Civil War (1861 - 1865).
Someone who gives backshots and openly grabs toilet paper residue from their partners ass.
Cholula: Yo I was dogging this girl and she had toilet paper crumbs in her ass, but I just picked it and slapped her ass to keep the mood going
Joel: Man you’re a fucking cotton picker dog