A turning mark shown while something is underway. It reports that time is passing, not that progress is being made.
Old English spinnan (to draw fibre out into thread by twisting), from Proto-Germanic *spinnan; the agent noun names the turning thing rather than the maker of cloth it once meant.
What tells a watcher that a process has not stalled, without making any claim about how close it is to finishing. Motion is the entire message; nothing here promises advancement.