The constructed language of Makhnovshchina
Outer Sign started as a simple gestural sign language among shipyard workers, asteroid miners, and other outer workers that had to spend a lot of time in space suits. Eventually, rough approximations of many of these gestures would be codified in a written form as graffiti on the walls of a lot of space ships and stations (usually originally in the bathroom). Probably the last thing to be added was a set of phonetic gestures for “spelling” in OS.