X-ray (English)

Where does "X-ray" come from?

The English noun 'X-ray' is formed from 'X' and 'ray'[1], serving as a calque of the German 'X-Strahl'[1]. The term was coined in 1895 by Wilhelm Röntgen upon his discovery of the rays, where 'X' signifies their unknown nature[1]. The component 'ray' descends via Middle English from the Old French 'rai', which comes from the Latin 'rādius'[2]. Later, the term expanded metaphorically in chess to describe control passing through a seemingly solid barrier[1].

Full etymology tree

X-ray (English), 'Short wavelength electromagnetic radiation usually produced by bombarding a metal target in a vacuum. Used to create images of the internal structure of objects; this is possible because X-rays pass through most objects and can expose photographic film.'
- compound X (English), 'The twenty-fourth letter of the English alphabet, called ex and written in the Latin script.'
- compound ray (English), 'A beam of light or radiation.'
  - inherited (Middle English)
    - inherited rai (Old French), 'beam; ray (of light)'
      - inherited radius (Latin), 'a staff, rod'
- calque X-Strahl (German), 'X-ray'

Ancestors

X (English)
ray (English)
X-Strahl (German)

Descendants and derived words

dual-energy X-ray absorptiometry (English)
hard X-ray (English)
soft X-ray (English)
X-ray absorbing glass (English)
X-ray astronomy (English)
X-ray binary (English)
X-ray crystallography (English)
X-ray diffraction (English)
X-ray fish (English)
X-ray fluorescence (English)
X-ray microscope (English)
X-ray photograph (English)

Sources

Updated September 2026

More words starting with X

Etymology data from Wiktionary, CC BY-SA 4.0 · About Miraris