A room near the rear of a premises, especially one that is only accessible to a privileged few and can be used as an inconspicuous meeting place.

Of, relating to, or happening in a backroom. / (figuratively) Characterized by secrecy or anonymity.

plural of backroom

The members of staff who work out of public view, such as the coaching team in a sports club.

(chiefly Britain) Someone who has an anonymous support role in an organization, especially a technician or scientist; a boffin.

plural of backroom boy