9. The term “popular piety” designates those diverse cultic expressions of a private or community nature which, in the context of the Christian faith, are inspired predominantly not by the Sacred Liturgy but by forms deriving from a particular nation or people or from their culture.
So the roots of piety, by definition, are to be found in culture, national or ethnic identity. Not the Mass, sacraments, or Hours. Still, Saint John Paul affirmed it:
Popular piety has rightly been regarded as “a treasure of the people of God”(John Paul II, Homily at the celebration of the Word in La Serena (Chile), 2, in Insegnamenti di Giovanni Paolo II, X/1 (1987), Libreria Editrice Vaticana, Città del Vaticano 1988, p. 1078.) and “manifests a thirst for God known only to the poor and to the humble, rendering them capable of a generosity and of sacrifice to the point of heroism in testifying to the faith while displaying an acute sense of the profound attributes of God: paternity, providence, His constant and loving presence. It also generates interior attitudes otherwise rarely seen to the same degree: patience, an awareness of the Cross in every-day life, detachment, openness to others and devotion”(Evangelii Nuntiandi 48).
My only concern about this citation is the presumption that piety is always to be found among the “poor and humble.” The implication is uneducated or not-catechized. But God is certainly to be found in everyday life outside of the Scriptures and liturgy by anyone who is attentive to a divine nudge.
By definition, “religiosity” covers the faith experience more generally: including Christianity, but not necessarily Christian:
10. “Popular religiosity” refers to a universal experience: there is always a religious dimension in the hearts of people, nations, and their collective expressions. All peoples tend to give expression to their totalizing view of the transcendent, their concept of nature, society, and history through cultic means. Such characteristic syntheses are of major spiritual and human importance.
Popular religiosity does not always necessarily refer to Christian revelation.
The full document, the Directory on Popular Piety and the Liturgy, is online at the Vatican site.