acetylene (n.)
gaseous hydrocarbon, 1864, from French acétylène, coined by French chemist Marcelin-Pierre-Eugène Berthelot (1823-1907) from chemical ending -ene + acetyl, which was coined from acetic in 1839 by German chemist Justus von Liebig; see acetic. Liebig's coinage was in reference to a different radical; acetyl was transferred to its current sense in 1850s, but Berthelot's coinage was based on the original use of acetyl.
The name acetylene is an unfortunate one as the hydrocarbon is not directly related to the modern acetyl radical and the molecule ... contains a triple bond, not a double bond which the suffix -ene (q.v.) implies. [Flood, "Origins of Chemical Names," 1963]