Placidus was the eldest son of the patrician Tertullus. When he was about eight years old, his father placed him under Benedict's care at Subiaco for education.
Gregory the Great (
Dialogues, II, vii) relates an account of Placidus being rescued from
drowning by his fellow monk,
Maurus, who, at Benedict's order, ran across the surface of the
lake below the monastery and drew Placidus safely to shore. It appears certain that he accompanied Benedict when, about 529, he removed to
Monte Cassino, which was said to have been made over to him by the father of Placidus. Of his later life nothing is known, but in an ancient
psalterium at
Vallombrosa his name is found in the
Litany of the Saints placed among the confessors immediately after those of Benedict and Maurus; the same occurs in
Codex CLV at Subiaco, attributed to the ninth century. ==Veneration==