Answer by Alex for How to delete history of last 10 commands in shell?

Maybe will be useful for someone.
When you login to any user of any console/terminal history of your current session exists only in some "buffer" which flushes to ~/.bash_history on your logout.
So, to keep things secret you can just:
history -r && exit
and you will be logged out with all your session's (and only) history cleared ;)