O / ostĭŏlum
noun

ostĭŏlum

gen. ostĭŏli · gender neuter · decl. 2nd
dim. ostium
a little door
a little door (post-Aug.), Col. 8, 14, 1: ostiola olitoria, Plin. 19, 8, 38, § 125: abscondita, Vulg. Dan. 14, 20.