pendulum (n.)

"anything that hangs down from a point of attachment and is free to swing;" specifically, in mechanics, "a body so suspended from a fixed point as to move to and fro by the alternate action of gravity and its acquired energy of motion," 1660, from Modern Latin pendulum (1643), noun use of neuter of Latin adjective pendulus "hanging down," from pendere "to hang, cause to hang" (from PIE root *(s)pen- "to draw, stretch, spin"). The Modern Latin word is perhaps a Latinization of Italian pendolo.