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Omar Khayyam, philosopher, mathematician, astronomer, wine specialist
and a poet (see The Rubáiyát of Omar Khayyám) went the distance while he
was working on algebra to unveil the numerical mysteries.
He referred to the unknown variable as "thing",
because no one had before thought about the variable deeply enough to need
to name it. The Arabic word for thing is "shay".
As in Turkish it is "sey". Khayyam went on using shay for the unknown
variable in the rest of his works.
In 756 A.D., when The Umayyad Caliphs conquered Andalucia, Spain,
scientific translations between Arabic and Spanish began, too. While Khayyam's
works were being translated, the translators couldn't make out what to do
with this word shay. In order not to manipulate Khayyam's original
idea, they decided to leave the word as it is. But in Spanish the vocalization
of "sh" could be written with the "x"
letter. So they came out with the word "xay"
to call the variable.
The further works and studies on mathematics and algebra in the western
world simplified the word xay into a single letter "x".
The unknown variable "x"...
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