In the case of American actress Halle Berry (1966-), it is from the name of a department store in Cleveland where she was born (the store was founded by brothers bearing the German surname Halle, a cognate of Hall).
We use a combination of data from the internet, and our own Machine Learning models to make these predictions.
In a gist, we use a Machine Learning model trained on a diverse global dataset of 100m+ names, and use it to predict different traits for a person based on first name!
NameGuessr guesses a person's nationality, age, and gender based on their name. We also try to give insightful info around the name's origin, name meaning, and name pronounciation.