To change your AirDrop name on Mac, open System Settings, click General then Sharing, and edit the Computer Name field.
On macOS Ventura and later, the setting moved into the redesigned System Settings.
If you're on Monterey or earlier, the route is slightly different.
People expect AirDrop to have its own name field somewhere, and it doesn't, which is why this trips so many users up.
Your Mac actually has two names, and it's easy to confuse them.
Read the complete breakdown, fixes and what happens next.