There's actually kind of a funny history behind the Eggplant emoji. Emoji are Japanese in origin and around the time they were taking off there was this Survivor like gameshow where one guy was confined to his apartment and he had to try and survive past the basics by applying for and winning sweepstakes items from various promotions from newspapers and magazines.

The participant's shortened form name was Nasu - which means "eggplant" so since the guy started the challenge with literally nothing including clothes they put a little Eggplant over his junk in post. That became a Japanese cultural meme that translated over once emoji became more widely adopted.

You probably won't see actual dick emoji in the actual set because emoji are an all ages access thing and exist on an international level. It's actually kind of funny how different cultures use the same finite set. Like in China how the angel emoji is construed as "I'm going to end you". One could see the things as becoming essentially a hieroglyphic set where they gain their own full individual linguistic meanings.