Life and Veneration
No biographical account of Onesimus survives. The sources record only that he was a monk who labored at the Kyiv Pechersk Lavra and that his relics are interred in the Near Caves of Saint Anthony. On this basis he is placed in the 12th to 13th century.
The general commemoration of the venerable fathers of the Near Caves dates to 1670, when the caves were restored following earthquake damage and the relics of a number of ancient ascetics were uncovered. Onesimus is numbered among the venerable monks of the Near Caves honored in this collective commemoration.