Mail (desktop) — change my sender name back to its original (iCloud not a factor)

How do I fix/change my sender name? I use Mail only on my desktop. I don't go through iPhone, iPad, or iCloud.

I want to change my sender name back to the original 'full name' set in Mail's Preferences, Account Information. This is the same name associated with my Apple ID, and my email address as shown in Mail's Windows menu, Previous Recipients. [On its own, Mail changed my sender name to that of a family member with an account to which I'm linked (I'm not sure which).]

Thank you!