Here's why:
* Pronunciation: French and English have different sounds and pronunciation rules. This often leads to name spellings being different even when they are meant to be the same name. For example, "Catherine" in English is "Catherine" in French, but the pronunciation is different.
* Origin: Many names have origins in different languages. Some names are popular in both French and English, but their spellings might vary because they were adopted from different languages. For instance, "Alexander" in English is "Alexandre" in French.
* Popularity: Some names are more popular in one language than the other. This can lead to different spellings being favored, even for the same name.
Here are some examples:
English | French
------- | --------
Alexander | Alexandre
Catherine | Catherine
David | David
Elizabeth | Élisabeth
John | Jean
Mary | Marie
Michael | Michel
William | Guillaume
To find out the correct French spelling of a name, it's best to consult a French dictionary or a reliable online resource.