Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
armāriŏlum, i, n. dim. [armarium], a little chest, or casket (ante- and post-class.): armariola Graeca, Plaut. Truc. 1, 1, 35.
A small cabinet, a bookcase, Sid. Ep. 8, 16; Hier. ad Matth. 3, 21.