What is the history of the variable names x and xs? [closed]

Answer 1

We can take the origins of x back much further, of course :-) François Viète (1540-1603) produced a book titled In artem analyticem isagoge (“Introduction to the Analytic Art”), which was the first work that systematically used letters to represent numbers.

Edit: Porges, below, points me to the really cool A History of Mathematical Notations by Cajori. To my pleasant surprise, the entire work is available online: http://archive.org/details/historyofmathema031756mbp

Answer 2

x is a common variable name in mathematics. xs is the plural form of x (get it?). In list pattern matching, x is one element, and xs is (generally) several.

Answer 3

x is the european transcription of the arabic word شيء (pronounce 'chi', or 'chaï'. or 'tchi', depending on the accent). This word means 'thing', or 'something' and was used by first arab and iranian mathematicians as a symbol to designate an unknown or unfixed value in a mathematical expression.

Back to these times, 'x' might have been considered by translators and european mathematicians as the closest approximation to this symbol of the unknown.