How to find the unix 'host' from the aws 'Endpoint'

I'm looking for the 'host' of an aws database server to use in this configuration option:

-h host
--host=host

Specifies the host name of the machine on which the server is running.
If the value begins with a slash, it is used as the directory for the
Unix domain socket. The default is taken from the PGHOST environment
variable, if set, else a Unix domain socket connection is attempted.

But all I can find is this 'Endpoint':

Endpoint: brendan.cp3s3jf32b9q.eu-west-1.rds.amazonaws.com:5432

Is that related? Is there any way to extract the 'host' from the 'Endpoint'?