When you use psql command prompt, system automaticly saves your prompts. If you use password when user creates operation, this situation can occur security risk. Therefore, you can delete this prompts with editing psql_history file like below.
Find And Delete psql Prompts
[root@pg ~]# locate .psql_history
/var/lib/pgsql/.psql_history
[root@pg ~]# vi /var/lib/pgsql/.psql_history