13" MacBook Air Terminal says " (base) UNKNOWN
The UNKNOWN part is your computer hostname, for some reasons it changed itself.
You can change the hostname from the Terminal using the following commands :
sudo scutil --set ComputerName &quot;newname&quot;
sudo scutil --set LocalHostName &quot;newname&quot;
sudo scutil --set HostName &quot;newname&quot;

Then flush your DNS cache with dscacheutil -flushcache and reboot your Mac.
You can also change it without using commands, in System Preferences &gt; Sharing &gt; Computer Name.