Flash-back to 2004 when Matt figured out how to change the computer name on his new Mac; now flash-forward to today when I need to do the same thing, and his method didn’t work. Also tried Richard Bronosky’s method, and still no joy.
If you have FiOS, it could be Verizon’s fault.
I needed to change the DHCP Client ID:
…and then I needed to rename the device at the router too, otherwise terminal would show my HostName as ‘new-host’ even after the above changes…
It’s possible I didn’t need to do all of these things, but I did anyways and finally got rid of that pesky ‘new-host’ name.