ש said to be the same as ش
Arabic šīn/sīn
In the Arabic alphabet, šīn is at the original (21st) position in Abjadi order.
Šīn represents /ʃ/, and is the 13th letter of the modern alphabet order and is written thus:The Arabic letter šīn was an acronym for "something" (شيء šayʾ(un) [ʃajʔ(un)]) meaning the unknown in algebraic equations. In the transcription into Spanish, the Greek letter chi (χ) was used which was later transcribed into Latin x. According to some sources, this is the origin of x used for the unknown in the equations.  However, according to other sources, there is no historical evidence for this.  In Modern Arabic mathematical notation, س sīn, i.e. šīn without its dots, often corresponds to Latin x.
In Moroccan Arabic, the letter ڜ, šīn with an additional three dots below, is used to transliterate the /t͡ʃ/ sound in Spanish loan words.
In Unicode, this is U+069C ڜ ARABIC LETTER SEEN WITH THREE DOTS BELOW AND THREE DOTS ABOVE.