The following information is from a post-em by Curt Hoffeman, curt_hofemann@yahoo.com:
Poppo, was count of the march in Thuringia from 880 to 892, when he was deposed by the German Carolingian king Arnulf of Carinthia. The family had been favoured by the emperor Charles the Fat, but Arnulf reversed this policy in favour of the rival family of the Conradines. [Ref: Wikipedia (who slightly rephrased it from the 1911 Encyclopedia Britannica online at: http://92.1911encyclopedia.org/B/BA/BABENBERG_FAMILY_.htm]