Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mūtītĭo or muttītĭo, ōnis, f. [mutio], a muttering, mumbling (Plautin.): quid tibi hanc curatio’st rem, verbero, aut mutitio? Plaut. Am. 1, 3, 21.