Perhaps from ragaz (in the sense of being suspended), a box (as a pannier) -- coffer.
see HEBREW ragaz
H712. argaz
אֶרְגַּז noun masculine box, chest, or like receptacle (compare Arabic a kind of (camel-) vehicle for women, also a garment containing stones, etc., as balance, makeweight (at side of haudaj); from above √, as swaying ? Syriac sack, Talmud אַרְגָּז chest, coffin); — ׳הָא 1 Samuel 6:8, 11, 15, compare HPS.