x

X · numeral, proper noun¹

Introduced by René Descartes in the context of mathematical notation, but has since widened to other contexts.

X · noun²

Presumably by abbreviation of the pronunciation of ecstasy.

X · proper noun³

1. Ancient Greek · borrowed fromΧ
2. English todayX

From Christ by abbreviation, orthographic borrowing from Ancient Greek Χ (Kh, letter chi), from Χριστός (Khristós, “Christ”).

X · noun⁴

From cross, due to the X symbol being a cross saltire.

X · proper noun⁵

Named after its predecessor, the W Window System; X follows W in the Latin alphabet.