A brief research is presented, about the origin and introduction in the portuguese geological nomenclature of the names "Carbonífero" and "Carbónico" to designate the respective geological System/ Period. The conclusion is that the term "Carbónico" is probably related with the proposal of Eugene Renevier (in 1874) for the creation of a Super-System named "Système Carbonique" containing the Devonian, Carboniferous and Permic. It was Wenscelau de Lima who introduced the terms "Carbonique" and "Carbónico" (in 1888) in the geological literature published in Portugal. Before that, other portuguese geologists had already used correctly the terms Carboniferous and "Carbonífero". Being Carboniferous (Phillips & Conybeare, 1822) the original proposition to formaly name the stratigraphic unit, and adopted by the international stratigraphic code, the natural translation to the portuguese language is "Carbonífero" as written by Pereira da Costa (1860-61), Bernardino Gomes (1865), Carlos Ribeiro and Nery Delgado (1867, 1876). Furthermore, the designation "Carbónico" is not in agreement with the recommendations of the international stratigraphic code.