Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
interpŏlātor, ōris, m. [interpolo], one who gives another appearance to things, a polisher, furbisher; a corrupter, spoiler (eccl. Lat.): multum est inter institutorem et interpolatorem, Tert. Spect. 2: veritatis, id. Apol. 46: Satanas totius saeculi interpolator, id. Testim. Anim. 3.