Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mōtĭuncŭla, ae, f. dim. [motio], a slight motion, shaking; in medicine, an attack of fever (post-Aug.), Sen. Ep. 53, 6: tentatus in Campaniā motiunculis levibus, Suet. Vesp. 24 init.