Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
nervōsĭtas, ātis, f. [nervosus], strength, thickness; of a thread, Plin. 19, 1, 2, § 9; of the body, Cael. Aur. Acut. 3, 18; id. Tard. 1, 4, 73; 5, 1, 21.