You have an anonymous user at localhost, with no password, with USAGE privilege only. IOW anonymous@localhost can connect, without a password, but can't do anything.
user BOREHOLES@% doesn't get seen when BOREHOLES logs in from localhost, because it's being masked by the anonymous@localhost, and can only login without a password.
So, you can do either (or both) of 2 things.
DROP user ''@'localhost';
FLUSH PRIVILEGES;
This will prevent BOREHOLES@localhost matching anonymous@localhost.
And / or
GRANT ALL on boreholes.* to 'BOREHOLES'@'localhost' IDENTIFIED BY PASSWORD 'boreholes_password';
FLUSH PRIVILEGES;
Specify the hostname that BOREHOLES can connect from.
Good luck,
Barry.