why "x" the unknown?

Terry Moore: why “x” the unknown?

Why the letter “x” represents the unknown? As we know that “x” a common thing in math class, but know everywhere we can find it such as: x prize, x file, project x, TEDx.

About six years ago, he decided to learn arabic that to be a supremely logical language. To write a word or phrase in Arabic is like crafting an equation every part carries a lot of information.

Little system in  Arabic call al-jebra, it means the system for reconciling disparates part. In English called al-gebra. The Arabic text containing mathematical wisdom. It came to europe such as spain in the 11 or 12 century, they interest to translate this wisdom into European language. but they got problem. The problem is there are some Arabic sounds don’t exist in European voice box such as “sheen” – “sh”, and it’s a first letter in the word “shay an” which means something, some undefined, unknown thing. We can make it definite with putting “al” at the first “al- shay an” (the unknown thing). This word exist in a mathemetic derivation of proof from 10^th century. The sound “sh” and the word “shay an” can’t be rendered into Spanish because Spanish doesn’t have it.

In a convention, they borrow “ck” sound from classical greek in the form of letter “kai (x)”. Later, this was translated into common European language or Latin, they simply replaced the greek Kai with the Latin X, it formed for mathemathical textbook for almost 600 years.

In conclussion, x represents the unknown because we can’t say “sh” in Spanish.