Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mĕrendo, 1, v. n. [1. merenda], to take an afternoon luncheon (late Lat.): merenda est cibus, qui declinante die sumitur, quasi post meridiem edenda: Hinc merendare, quasi meridie edere, Isid. Orig. 20, 2, 12.