'opalescent' originates from the Latin word 'opalus,' which referred to the gemstone opal, known for its iridescent colors.

'Opalus' transformed into the French word 'opale,' and eventually became the modern English word 'opal,' from which 'opalescent' is derived.

Initially, it referred to the gemstone's unique color play, but over time it evolved to describe anything with a similar iridescent quality.