A closed circle, and the sounding of a bell. Both are things that return to themselves.
Old English hring (a circular band) and the separate verb hringan (to sound, ring a bell), both from Proto-Germanic roots; two old words sharing one modern spelling, one naming a closed shape and the other a returning sound.
A closed circle and the sound of a struck bell, carried by one word — a shape that returns to itself, and a sound that does the same.