The most common term for “tree” in MTjŠ and the only one in the SAE volumes (see Kogan 523-524 for examples). Not attested in MTO almost certainly borrowed from Arabic (Kogan 2015: 43)
Likely an Arabism.
Qishn, * ṯ > t. Meaning shift 'perineum' > 'anus' > 'bottom'?
A reflexive stem of the PS prototype.