From an unused root meaning to pulverize; a mill-stone -- mill (stone).
H7347. recheh
[רֵחַה] noun [masculine], only
dual רֵחַיִם (hand-)mill (probably = two mill-stones); — ׳ר absolute, common household utensil, turned by maids, Exodus 11:5 (הָרֵחָ֑יִלם; J), female slaves Isaiah 47:1 (with טָחַן, q. v.); בָּר ׳טָחַן Numbers 11:8 (J); ׳ר וָרָ֑כֶב Deuteronomy 24:6 (see רכב); ר ׳קוֺל as sound of family life Jeremiah 25:10.