The story
From the theoreticians who predicted this effect, astronomers James E. Gunn and Bruce Peterson, which creates a lack of radiation at a span of wavelengths.
Etymology from Wiktionary, CC BY-SA 4.0.
Gunn-Peterson trough
Today it means: A feature in astronomical spectrometry of distant light, caused by the Reionization Era's absorption of UV light, leaving a gap in the spectrum. Full definition →