leśny dziadek

Etymology
Unclear; either from, a forest creature in Slavic mythology, or from Polish guerrilla fighters in World War II that operated mainly in forests and kept reminiscing about their past after the war.

Noun

 * 1)  fossil; old person in a position of authority stubbornly sticking to anachronistic views, no longer competent for their job and not willing to step down to make way for the younger generation