ergastŭlārĭus — Lewis & Short
ergastŭlārĭus, a, um, adj.ergastulum,
I of or belonging to a workhouse or house of correction (late Lat.).
I Adj.:
servus,Amm. 14, 11 fin.—Also:
in tenebris ergastularibus,Sid. Ep. 7, 9.—
II Subst.: ergastularii, ōrum, m. (sc. servi), overseers of a penitentiary, Col. 1, 8, 17.