A Latin word meaning breastplate, Lorica is a type of prayer recited for protection. It comes from the early Christian monastic tradition, though some lorica may have older pagan roots and resemble charms used by pagans.
Brigit Bé Bithmaith / Brigit's Lorica (9th century) Irish
Fáeth Fiada / St Patrick's Breastplate (5th-8th century) Irish
Lorica of St Fursey (7th century) Irish
Alexander's Breastplate (10th -14th century) Welsh
Lorica of Gildas / Lorica of Loding
Lorica of Columba / Lorica of Mugron
Aldhelm’s Lorica (1st century) Saxon [Riddle]
Circles are believed to have protective properties because they lack corners. Corners are considered to be a type of thin place. where energy, supernatural entities, and people might pass through. By it's very nature therefore, circles serve as the perfect trap.
Celtic folklore: If you want to trap a druid, put him in a round room.
An ABCs of Gods, Myths, and Superstitions.