Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ănĭmŭlus, i, m. dim. [animus], only in the voc. as term of endearment (cf. animus, II. B. 2. f.): Mi animule, my heart, my darling, Plaut. Cas. 1, 46: Animule mi, id. Men. 2, 3, 11.