My father told me that the hand gesture, commonly associated with Star Trek as the Star Trek hand signal, was actually first used as a way to distinguish Jewish people from non-Jewish people. He said that if you are able to successfully make this hand signal, since some people cannot, then that was a way to tell whether or not you were Jewish. He had heard this from his cousins, who are Jewish, and who are all able to make this hand signal.
He does not actually believe that this is true, but he found it funny and has remembered it since the time he heard it from his cousins, years ago. He also really likes the Star Trek series, and the fact that this hand signal was used in this series reminded him of what his cousins had told him.
Most people replicate this hand signal when they are mimicking the Star Trek hand signal, because this is what it is most popularly known as. Other than that, I do not recall seeing this hand signal being used in other contexts or conversations.
I find what my dad’s cousins had learned this hand signal to symbolize funny. I think that they must have heard that rumor from one of their friends, or possible a relative, that was just joking with them about this. I do not believe that this was an original meaning for this hand gesture.