'X-ray' originates from German, specifically the word 'X-Strahlen,' where 'X' denoted an unknown type of radiation and 'Strahlen' meant 'rays.'

'X-Strahlen' transformed into the English word 'X-ray' and eventually became the modern English term 'X-ray.'

Initially, it meant 'unknown rays,' but over time it evolved into its current meaning of 'a type of electromagnetic radiation used for imaging.'