I have one DD with an exceptionally popular name - as in top ten for many, many years. I had no idea it was popular when I chose it - it was a name with lovely associations for me.
I became aware of its popularity when I took DD out to parks, swimming, etc. But it didn't matter. She was my little "Cleopatra" iyswim. She had also developed a very cute mispronunciation for her name by that point, and that was what we called her.
When she went to school she was officially "Cleopatra K" and the other one in her class was "Cleopatra R", but they were known by different abbreviations and still are.
Weirdly, her next younger sister has a name that was way down the lists in the 600s, and on her first day of Kindergarten, lo and behold, we met the only other girl with that name we have ever encountered. Again, a "Gwendolene K" and "Gwendolene R" situation, but different abbreviations used.
So there are no guarantees.
- Names changed but you get the gist...