Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
tĕnē̆brĭo, ōnis, f. [tenebrae], one who shuns the light, a trickster, swindler (ante-class.): tenebrio Tyrius, Afran. ap. Non. 19, 4 (Com. Fragm. v. 109 Rib.); Varr. ib. 6 and 13.