Algebra has its roots in the Middle East where sciences including mathematics and astronomy once flourished in the Islamic world. Muhammad al-Khwarizmi was one of the major mathematicians of his time and the author of a number of influential books. His book on algebra is titled "Kitab al-jabr wal-muqabala" which translates to "the book of calculation by completion and reduction." The Arabic word "al-jabr" is the origin of the word "algebra" which describes the process of moving terms from one side of an algebraic equation to the other to find the value of an unknown.
So why do we use x in Algebra.
Well…from the 11th to 13th centuries, Europe absorbed, learned and rediscovered immense knowledge from Islamic civilization. Islamic textbooks were translated into Spanish, Greek and Latin.
The Arabic for “something” (some specific undefined thing) is…
This word is pronounced ‘shee’…or Al shee, as it is written above. However the sh sound that is very hard to pronounce in Spanish. Arabic is also a very precise language, and creating an exact translation of Arabic words is difficult. So Spanish scholars, trying to translate from Arabic, decided to use a Greek letter…
They chose the letter chi…pronounced kai. Which then became X when the texts were translated in Latin…and remained X when translated again into English!