Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
frīgor, ōris, m. [frigeo], cold (late Lat.): molestissimus, Theod. Prisc. 2, 29.
Also, frigdor (contr. from frigidor, from frigidus], Theod. Prisc. 2, 16; id. de Diaet.