Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Sub -ballĭo, ōnis, m., Under-Ballio, Sub-Ballio; a comically-formed name: Ha. Tune es Ballio? Ps. Immo vero ego ejus sum Subballio, Plaut. Ps. 2, 2, 13.