I think it's a pretty common gesture, maybe meaning roughly "you won't believe this," or "I'm slightly breathless with amazement." My four-year-old actually does this gesture when describing something amazing, and I don't see myself or my wife doing it.
But gestures are so hard to translate. I grew up in Italy, famous of course for its gestures. One of the most common is making an "OK" symbol with your fingers and drawing little short straight lines downwards with it. What does it mean? I doubt many of the people using it could put it into word, precisely. But we learn it the way we learn language, the same way we use intonation to turn a statement into a question, without it ever being taught.
But gestures are so hard to translate. I grew up in Italy, famous of course for its gestures. One of the most common is making an "OK" symbol with your fingers and drawing little short straight lines downwards with it. What does it mean? I doubt many of the people using it could put it into word, precisely. But we learn it the way we learn language, the same way we use intonation to turn a statement into a question, without it ever being taught.