radon

from the name of the element radium because the element radon results from the decay of radium. This name was given in 1923, but it was first named radium emanation or emanation (which gave emanon) by its discoverer Friedrich Ernst Dorn in 1900, then niton by William Ramsay and Robert Whytlaw-Gray who isolated it in 1908. Initially, the term radon referred only to radon-222, an isotope produced by radium-226.