September is the month of the Sorrowful Mother (also Her Seven Sorrows/Dolors).

January - The Holy Name of Jesus
February - The Holy Family
March - St. Joseph
April - The Blessed Sacrament / Holy Eucharist
May - The Blessed Virgin Mary
June - The Sacred Heart of Jesus
July - The Precious Blood of Jesus
August - The Immaculate Heart of Mary
September - The Seven Dolors of Mary / The Sorrowful Mother
October - The Holy Rosary
November - The Holy Souls in Purgatory
December - The Immaculate Conception

Better late than never...

The Seven Sorrows
1) The Prophecy of Simeon (Luke 2:34-35)
2) The Flight into Egypt (Matthew 2:13-21)
3) The Loss of Jesus for Three Days (Luke 2:41-50)
4) The Meeting of Jesus and Mary on the Road to Calvary (John 19:17)
5) The Crucifixion of Jesus (John 19:18-30)
6) Jesus Taken Down from the Cross (John 19:39-40)
7) Jesus Laid in the Tomb (John 19:39-42)

It is said by many that by meditating on these sorrows, Our Blessed Mother will help you by revealing to you areas in your life or sins that are preventing you from drawing closer to Her Divine Son.

One such devotion to Our Lady under this title is the Seven Sorrows Rosary or Servite Rosary. I learned of this particular devotion years ago on a retreat (Ignatian) led by the priests of Miles Christi. Highly recommend the retreat.
https://7sorrowsrosaries.com/pages/how-to-pray-the-seven-sorrows-rosary-of-mary

Personally, I prefer this meditation. Fairly short, and I have had certain sins/tendencies revealed to me that are hindering my own growth in holiness.
https://www.ewtn.com/catholicism/library/seven-dolors-of-the-blessed-virgin-mary-5437

Overall, I highly recommend this devotion. I believe it was Our Lady under this title that intervened 23-24 years ago in a personally drastic way to pull me out of the pit of grave sin. That night is still crystal clear. Dumb sinner that I've been, it's taken me a great many years to realize the particular title.