The problem for the Medieval Spanish scholars who were tasked with translating this material is that the letter sheen and the word shayun can't be rendered into Spanish because Spanish doesn't have that SH, that "sh" sound.
O problema para os académicos medievais españois que tiñan que traducir este material é que a letra SHeen e a palabra shalan non se poden reproducir en español porque o español non ten ese SH, ese son do "xe".