Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. Cācus, i, m., = Κᾶκος, son of Vulcan, contemporary with Evander, a giant of immense physical strength, who dwelt in a cave on Mount Aventinus, and troubled the whole region around by his robberies; he robbed even Hercules of the cattle of Geryon, and was on that account slain by him, Ov. F. 1, 543 sq.; Liv. 1, 7, 5 sq.; Verg. A. 8, 190 sq., and Serv. in h. l.; Prop. 4 (5), 9, 7; 4 (5), 9, 16; Col. 1, 3, 6; Juv. 5, 125; Sol. 1, §§ 7 and 18.
2. căcus, i, m. [perh. κακός; cf. Engl. villain, rascal, as designations of a servant], a servant, Inscr. Vellerm. 7, 1, 27.