How to say "vow" in Arabic

נדר and nadhr point to the same root — though the consonants don't line up perfectly: native Hebrew usually turns this Proto-Semitic sound into ז (as in זאב matching ذئب), but here it's ד, most likely because Hebrew נדר arrived alongside Aramaic נְדַר, which regularly has ד. Same vow, a well-traveled root.