Scapulars, as in the monastic garment generally, have been in use since the 7th century. There are a large number of different colors and types of scapulars associated with different orders and devotions. The Brown Scapular is the one we are talking about here.
Regarding Our Lady “elevating” the scapular “with a promise of salvation”, as we have explained above, it is no longer taught as fact that Mary gave the scapular to St. Simon Stock or appeared to him in a vision.
Nor is it taught nowadays that Mary will take all the souls of Scapular wearers to heaven on the Saturday after their death, etc.
One wears the scapular piously as a sign of devotion to Mary and one can have hope in her intercession, but there is no “promise of salvation” for wearing it.