antetynym

Noun, from Greek anti "opposite, against", Greek étumon "true sense", and Greek ὄnyma "describing types of word or name"
A word or phrase that has a counterintuitive or unexpectedly opposite meaning
Pronounced: Ant Eti Nym

Akili: You want some of this Gorilla Dick?

Narrator: Gorillas have some of smallest penises of all primates, despite being quite large in stature and bulk. Penises similar to those of the Gorilla would not be what most human women would want. Gorilla Dick is a Antetynym.