Pope Formosus
"Panisperna" most probably refers to the tradition of the Poor Clares of the adjacent convent distributing bread and ham, "pane e perna" on 10 August, the Feast of St. Lawrence, in remembrance of his distribution of funds of the Church to the poor. The previous name of the church "in Formoso" referred to Pope Formosus who erected the first attested church on its site.