Friedrich Oskar Giesel called the substance he found “emanium.”
Giesel encountered the substance in 1902 while working with radioactive material derived from pitchblende. He isolated a lanthanum-like fraction and, after further study, named the proposed new element emanium in 1904. Later comparisons showed that Giesel’s emanium was the same element now known as actinium.
The naming history is complicated because André-Louis Debierne had announced actinium earlier, in 1899. Since Debierne’s name had priority in the conventional account, “actinium” was retained rather than replacing it with “emanium.” Giesel nevertheless made important contributions, including preparing radiochemically pure actinium and identifying its atomic number.
Modern historical analysis has questioned exactly what Debierne’s earliest samples contained, and some researchers have argued that Giesel deserves greater credit for the discovery. For a standard quiz, however, emanium is the distinctive name associated with Giesel’s actinium-like substance.