“Saint Patrick’s Breastplate” is an ancient Irish prayer traditionally attributed to the fifth-century Saint Patrick himself. The title reflects the medieval custom of knights who placed inscriptions of prayers in their breastplates and then recited them as they rode into battle. So strong was this association that one of the hymn’s alternate titles – Lorica, Latin for “breastplate” – came to be used broadly for any prayer for protection.

Over the centuries, many myths sprang up around this poem.