The stereotype of black people having longer labia and larger penises, and being fetishized or stigmatized on that basis, is dynoirism, misogynoirism, andronoirism, and internoirism.
Firstly, both stereotypes come from the idea of "large genitals = masculine"* and that black people are "inherently masculine" compared to white people.
*(Which is also intersexist. People on the agenital spectrum are not "inherently less masculine" nor are people with clitoromegaly or pseudophallus "inherently more masculine". And obviously black people can be on the agenital spectrum too.)
Secondly, when it comes to the labia stereotype, it likely stems from African cultures who would practice labia stretching as a part of their culture.
And thirdly, it promotes this idea that labial hypertrophy is "negative" in non-black people who are socially imposed as female. And since white people are put as a beauty standard for black people, it makes black people in turn think "oh, these white people want smaller labia, so I should want that too, right?" - which means black people with labial hypertrophy are either fetishized, masculinized, or made to feel ugly.
(Dynoirism is the intersection of anti-blackness and dysexism. Dysexism is oppression towards dysex [link] people.)
