Etymologically uncertain. The plural form with -ṣ- suggests the diachronic priority of *ṣ in this word. Leslau (LS 346) tentatively considers Arb. ṣidār- ‘a garment of which the upper part is covering the head and the lower part of which covers the breast an the shoulders’ or ṣadriyyat- ‘espèce de gilet, de camisole, de chemisette sans manches’. Note that the former term is an Iranian loanword (Neo-Persian čādar) which also penetrated JBA as ṣadrā ‘coarse garment’ (DJBA 952, with an extensive etymological discussion).