An armband was a device or a piece of material which was worn around the arm, over the sleeve of other clothing if present. Members of the Nazi Party and the Cult of the Pah-wraiths both wore armbands as part of their uniforms, to show the allegiance of the wearers. (TOS: "Patterns of Force"; DS9: "Image in the Sand ", "Covenant")
Nyota Uhura once wore a black fabric armband at her communications station on the bridge of the USS Enterprise in 2267. (TOS: "The City on the Edge of Forever")
Technological armbands were worn by crewmembers from the USS Voyager, while surveying Makull's homeworld in 2371. (VOY: "Time and Again")
These 24th century armbands are not named on screen; their designation as "armbands" comes from the script of "Time and Again".