With its long, ambiguous history and multiple phonemes, the letter X is quite a dark horse. It can mean Christ, like the X in Xmas, stand for a chromosome, and even show up in friendly and amorous correspondence (XOXO).
But, how did X end up in the alphabet to begin with?
The origin of X
Since its inception, the letter X has struggled to establish its own identity, so it may be no coincidence that X is commonly used to represent the unknown in both language and mathematics. But, how was it created?
X is derived from the Phoenician letter samekh, meaning “fish.” Originally used by the Phoenicians to represent the /s/ consonant (denoting a hard S sound), the Greeks borrowed the samekh around 900 BC and named it Chi.
The ancient Greeks utilized their newly acquired phonological element to simplify the digraph (“a pair of letters representing a single speech sound”) /ks/, which is used most prominently throughout the western regions of Greece.
The Romans later adopted the X sound from the Chalcidian alphabet, a non-Ionic Greek alphabet, and borrowed the Chi symbol, consisting of two diagonally crossed strokes, from the Greek alphabet to denote the letter X as well as to identify the Roman numeral X or “10.”
So to sum up: The Romans took the /x/ sound from one alphabet (Chalcidian) and combined it with the Chi symbol from another alphabet (Greek) and thus X was born.
WATCH: Where Do “XX” And “XXX” Come From?
How to say X
Like many letters in the English language, such as C and J, X is a bit of a phonetic chameleon. For instance, X is used to establish the /ks/ sound, as in wax and fox—referred to as a “voiceless velar fricative,” in case you were really wondering. This articulation is made by placing the back of the tongue at the soft palate.
The same rule applies for X’s /gz/ sound, as in auxiliary and exhaust. X can also take on the /z/ sound as in xylophone and Xanadu, the hard /k/ sound as in excite, and /kzh/ as in luxury. The X can also be silent as in Sioux (Falls), and the French loan-word faux.