Star Trek fought for ethnic and gender diversity.
Star Trek presented more than 50 years ago a utopian future where there are good relations and equality among all, regardless of ethnicity or gender. In short, it was one of the forerunners in promoting diversity. The character of Lieutenant Uhura encompasses all of this. She is a woman, African-American, and has a vital role in the series as an essential part of the team’s functioning.
Of course, this hand gesture means "read between the lines"...
He came up with it for the character. He's the reason it's in the show. That's all that anyone needs to know. Pointy ears weren't a new thing, either.