*riḥay- - hand-mill, millstone (LS 397; Fronzaroli 1972:633; HALOT 1216)

Akkadian

erû, irû - grinding slab, hand-mill (AHw. 247; CAD E 323)

It's hard to explain the initial e-. One wonders if the word is related to the Sum. e₂-ar₃-ar₃ (Attinger, Glossaire 415).

Ugaritic

rḥm - (du.) millstone (DUL 724)

Hebrew

rēḥayim - (du.) millstone (BDB 932; HALOT 1216)

Syriac

raḥyā - mill, mill-house, millstone (LSyr:723; SL 1455)

Arabic

raḥan - mill, millstone (Lane 1057)

Mehri

ərḥā - hand-mill (ML 322)

Jibbali

ráḥaˀ - hand-mill (JL 210)

Harsusi

reḥáˀ - hand-mill (HL 104)

Soqotri

rᵉḥa - rotating hand-mill (two slabs on an axis) (LS 397; CSOL II 564)