That would be a maniple. It’s my understnading that its origin evolved from what used to be a purificator (the white linen used to cleanse vessels and wipe the rim of the chalice) that hung over the priests arm. Maniples started evolving and did not always evade the poor design of vestments in the early 60’s. Some became rather long, and I have heard stories of them knocking over chalices. This all said, I don’t know exactly what the reason was for its supression, or that it has been supressed. I just know that its not required.
Pax Domin,
Casey the Seminarian