I think the Google Earth installation is not unrelated. I remember experiencing something
like this on my systems, not only with Google Earth (e.g. Vivaldi, Skype for Linux) and
the culprit was apparently the Gnome Keyring library (a GNOME analog of TDE Wallets, but
there is only one wallet and its password is the user's password) which is used by
some software to store keys, etc.
Google Earth seems to store some API-specific data it uses to connect to Google servers in
the Keyring.
Normally the keyring gets automatically unlocked on logon without the user even noticing.
Sometimes it doesn't. This happens when the appropriate service (don't remember
which) is not started upon startup. Then, the first time access is requested by one of the
applications, this prompt shows. It certainly seems like this happened in your case.
Hope this helps to find the solution.
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Mavridis Phlippe