Peter, I think this is the trail of an artificial Earth satellite - a very faint one - that is, very small. The trail ends because the satellite moved into the FOV near the end of the exposure (or vice versa left at the beginning), or it moved into (or emerged) from the Earth's shadow. The trail is wiggly either because the satellite is tumbling, though you might expect to see more variation in the intensity, or because there was atmospheric turbulence which gets integrated out of the longer exposure on the target and the stars.