John Saward has an excellent article on courtesy in the ETWN document library.

Courtesy is not strictly distinct from the other virtues, but rather a quality to be found in them all. It has something to do with reverence, humility, and chastity. It is shaped by charity, the form of all the virtues, into the quality of mercy. It is the beauty of a brave and generous life.

So reverence, humility, chastity, charity, mercy and beauty all go into making up a courteous man.  And of course, for all Christian courtesy to exist, namely that courteous quality of mind that is directed ultimately to the worship of God, all of these virtues are motivated by faith in Christ and love for God.

Courtesy is not merely the refusal to step out of the bounds of accepted manners, or even to do unto others as one would wish them to do unto him:

The courteous person has an attitude of “worship” toward his fellows: by small deeds of kindness, he acknowledges their worth, their dignity, as human persons. In the Sarum marriage rite, the husband vows reverence and thus courtesy toward his wife in the very acts of married love. “With my body I thee worship.” Chivalrous respect is of the very essence of husbandly love.

“Worship” here has the archaic connotation of reverence, which is to all those for whom Christ died.  No one should be excluded.  Christ came to serve.  He died for the many.  He wills that all men be saved.  True reverence for other men, especially our enemies is the spirit of Christ which wishes life upon all sinners.

St. Maximilian prayed not only that the Freemasons would be thwarted in their efforts to destroy the Church, not only for their conversion, but that they would become servants of Our Blessed Lady.

Which brings me to the Marian character of courtesy.  Saward says:

When we look at the artistic images of the Annunciation in the 15th century, the great age of courtesy, we find all the tell-tale signs of courtesy. In a painting by Fra Filippo Lippi in the Uffizi, Gabriel bends his knee and bows his head in the presence of the Holy Virgin, and his arm appears to strike his breast as if to say, ‘Madonna, my Lady, I am not worthy to come under thy roof.’ In fact, in all of the iconography of Christendom, the angels of God are courteously content to keep their wings in the wings and leave center-stage to the God-Man and his human saints. In the angels, person and mission are one–the very name “angel” describes an office,
not a nature. Everything in the angelic world is centered on God. Self-effacement and thus courtesy are the secret of the angels.

The Courtesy of our Lady Our Blessed Lady, God’s Mother and ours, is medieval man’s first thought when he hears the word “courtesy.” She is the object of the courtesy of Gabriel and Elizabeth, but among creatures she is also the virtue’s most perfect embodiment. Here is
incandescent purity, sublime humility, the most tender motherly mercy. If courtesy is self-emptying, then no created person is more courteous than she whose every thought, word, and deed is centered on her son. “Do whatever he tells you.” In Pearl, the Gawain poet finds
the soul of his little daughter in the presence and service of the Queen of Courtesy, “Matchless Mother, Merriest Maid, Blessed Beginner of Every Grace.” Our Lady is the Church’s supreme model in courtesy, as she is in everything that is Christian.

Now it would be a crass error to see the devotion of medieval man to heaven’s Queen as a mere transposition of the courtly honor he paid his earthly mistress. On the contrary, the veneration of Mary was a constant source of renewal and purification. It challenged men to love and look upon women in a more than merely erotic way. She who is uniquely both Virgin and Mother somehow cast her radiance upon all those who were separately virgins and mothers. There is a whole genre of writing that sings the spiritual beauty of women for the sake of the Mother of God. According to a 15th- century ballad, this Mary inspired courtesy toward women graced the life of Robin Hood.

Robin loved Our dear Lady;
For fear of deadly sin
Would he never do company harm
‘That any woman was in.

Don’t forget when we say “Our Lady,” (Domina Nostra), it implies both a reverence for her queenship and her femininity.  She is the ideal woman, and the Queen of Courtesy.