From Proto-Italic *fworom, from earlier *θworom, from Proto-Indo-European *dʰwor-om (“enclosure, courtyard, i.e. something enclosed by the door, or the place outside, i.e. through the door”), from *dʰwer- (“door, gate”).
Cognate with foris, forās, Old Church Slavonic дворъ (dvorŭ, “court, courtyard”), Sanskrit द्वार (dvā́ra, “door, gate, passage”) and Lithuanian dvãras (“estate”).