It is a devotion of the Order of the Servants of Mary…the Servite Friars, Nuns, and Third Order Regular and Secular. It is the Servite Rosary in complement to the Servite Scapular, the Black Scapular of Our Lady of Sorrows.
You can visit the Servite website for additional material to read.
Curia Generalizia in Rome:
servidimaria.net/sitoosm/en/
USA:
servite.org/
United Kingdom & Ireland:
servitefriars.org/
The Servites, I should add, run the Pontifical Institute for the study of Mariology in Rome.
I was invested with the Servite Scapular many years ago. (It is not limited to their Third Order Secular but is extended to their Confraternity of Our Lady of Sorrows.) The Servite Rosary is one I love to say…particularly in Lent or on Fridays…or on her feast day.
This article might also be of use; it is substantially correct.
aleteia.org/2016/09/15/how-to-pray-the-chaplet-of-the-seven-sorrows-of-mary/
I will add that this is a devotion spoken about in the approved apparitions of Our Lady at Kibeho. That is likely a reason why you are experiencing confusion as to its origin. The emphasis of those following in this apparition can reflect more the aspects of the apparition than the historic Servite origin of the devotion.
I hope this is of help.