From Old East Slavic двьрь (dvĭrĭ), inherited from Proto-Slavic *dvьrь, which traces back to Proto-Indo-European *dʰwer- ("door, gate"). Cognates span the entire IE family: Latin foris, Greek θύρα (thýra), English door, German Tür, and Sanskrit द्वार (dvāra). The root originally referred to a double-leaf gate, reflected in the dual/plural forms still preserved in some archaic expressions.

In Russian superstition, sitting or standing in a doorway (на пороге) is considered bad luck — the threshold is a liminal space between worlds, and lingering there was believed to invite misfortune or illness. Russians may politely ask guests not to talk through a doorway. The phrase «ломиться в открытую дверь» (to break down an open door) is a common idiom meaning to argue for something that is already obvious or agreed upon.