So, according to Terry Moore, Spanish translators used the Greek K and later the X for the word " شيء " [šæy’], the algebraic 'x' or 'unknown'. He pronounces " شيء " [šæy’] as "shay".
Hmm...
That word " شيء " [šæy’] in those ancient days was not necessarily pronounced like the English "shay". (It has to do with 'isoglosses')
It more than likely contained a harsh rasping laryngeal H [χ]. Thus the word started with "sχ" (as in the Dutch Scheveningen [ˈsχeːvənɪŋə(n)]). There is still a mathematical Dutch word 'verSCHIL' (difference) that has its etymological root in " شيء ".
The "χ" in Greek is the harsh sound "chi" and is represented by the Greek letter X.
So when Moore says that the Spanish did not have a sound for " شيء " (which was then more than likely pronounced as šχæy’), and that they used "cK" instead, he was wrong AND half right. He refined his statement a little later by saying that they used the "K" which then became an X.
So, Moore is wrong AND half right:
- wrong for the " شيء " that sounds like "shay",
and
- half right for the "K" that was actually a "X".
(Although it is true that the K ilooks like an X in Latin script.)
Of course all mathematicians are wrong as they should have said:
X (CHI)
instead of
X (EKS)!
But they can blame the Spanish.
So, Terry Moore's explanation is not as complete as he makes it sound. Nevertheless I liked it a lot.