# Why $x$? Why mathematicians have started using the names of the variables from the end of the alphabet? [closed]

Does anybody know why traditionally has been the letter $x$ used as the incognita in an equation? And then following back: $y, w, \dots$

Why starting from the end of the alphabet?

• Maybe it's because the first letters of the alphabet were already used for constants? – Bram28 Aug 15 '18 at 15:15
• While questions about the history of mathematics are not off-topic here, I think that you are more likely to get a good answer if you ask the question on History of Science and Mathematics. While there is no clear consensus about what kinds of questions are more appropriate for that site, my reading of the discussion is that questions that are connected to other branches of science (as this one, I think, ultimately is) and questions that don't require deep mathematical knowledge (as this one does not) should, perhaps, be migrated. – Xander Henderson Aug 15 '18 at 16:36

Regarding $x$ there was a TED talk by Terry Moore: Why is 'x' the symbol for an unknown?, who claimed it came from the Arabic word al-shalan, which means "the unknown thing".