Va-et-vient.
ETYM Also shittle, Old Eng. schitel, scytyl, schetyl; cf. Old Eng. schitel a bolt of a door, AS. scyttes; all from AS. sceótan to shoot; akin to Dan. skyttel, skytte, shuttle, dial. Swed. skyttel, sköttel. Related to Shoot, Shittle, Skittles.
1. A bus or train or airplane that plies back and forth between two points.
2. Passes the weft thread between the warp threads.