Where does “dui” come from?

dui (Romani) comes from Sanskrit द्व, from Proto-Indo-Iranian dwáH, from Proto-Indo-European dwóh₁ — two.

Ancestry of “dui”, step by step

StepLanguageWordMeaning
1Sanskritद्वtwo, both
2Proto-Indo-IraniandwáHtwo
3Proto-Indo-Europeandwóh₁two
Every word from Proto-Indo-European dwóh₁ →Every word from Proto-Indo-Iranian dwáH →Every word from Sanskrit द्व →