When I receive in my inbox a notification regarding my new WordPress website (she just rises), the sender is the name of one of my previous websites (back to the Hamptons).
The output there is probably related to your local address book for e-mail addresses. Take a look at the details of the email to see if the sender’s name comes from your local address book.
The local address book is what your email service provider Gmail apparently provides for you. You can read more about this here in their FAQ: https://support.google.com/contacts/answer/7280886 – the email you mentioned must be somewhere there, and the old name for it will probably be stored there.