Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
inceptor, ōris, m. [incipio], a beginner (anteand post-class.): o mearum voluptatum omnium inventor, inceptor, perfector! Ter. Eun. 5, 8, 4: carminis, Avien. Arat. init.