Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
‡Matrae, ārum, f.(dat. plur. MATRABVS, for Matris, Inscr. Grut. 29, 1), or Matres,more freq. Matronae,the protecting goddesses of a country, city, or place:MATRIS AVGVSTIS D. D., Inscr. Grut. 90, 1; so ib. 2 sq.