Here’s some history of the Chaplet of St. Michael the Archangel courtesy of EWTN’s site.
The Chaplet of St. Michael is a wonderful way to honor this great
Archangel along with the other nine Choirs of Angels. What do we
mean by Choirs? It seems that God has created various orders of
Angels. Sacred Scripture distinguishes nine such groupings:
Seraphim, Cherubim, Thrones, Dominions, Powers, Virtues,
Principalities, Archangels and Angels (Isa. 6:2; Gen. 3:24; Col.
1:6; Eph. 1:21; Rom. 8:38). There may be more groupings but these
are the only ones that have been revealed to us. The Seraphim is
believed to be the highest Choir, the most intimately united to God,
while the Angelic Choir is the lowest.
The history of this Chaplet goes back to a devout Servant of God,
Antonia d’Astonac, who had a vision of St. Michael. He told Antonia
to honor him by nine salutations to the nine Choirs of Angels. St.
Michael promised that whoever would practice this devotion in his
honor would have, when approaching Holy Communion, an escort of nine
angels chosen from each of the nine Choirs. In addition, for those
who would recite the Chaplet daily, he promised his continual
assistance and that of all the holy angels during life.