She is named as Madame Eglantine and wears a golden brooch inscribed with the letter 'A' and the phrase itself as appears in line 162 of The General Prologue of The Canterbury Tales:
Of smal coral aboute hir arm she bar
A peire of bedes, gauded al with grene,
An theron heng a brooch of gold ful sheene,
On which ther was first write a crowned A,
And after Amor vincit omnia.
The Prioress's Tale from a painting by Edward Coley Burne-Jones |
Love = amor (noun)
Vincit = conquers (verb)
Omnia = all (adverb)
The full phrase comes from Virgil's Eclogues: 'Omnia vincit amor: et nos cedamus amori' and translates as 'Love conquers all: let us too surrender to love'.
It's significance is an insight into the character of the Prioress who is portrayed as a social climber with outward signs that are at odds with the simple piety of her tale and position, such as her (incorrect) French accent, jewellery and the ambiguity of meaning of this phrase which more commonly relates to courtly than God's love.