Slip Yoke/Slip Spline
WARNING: This page is about a different car, the 2005 Ford RV Cutaway, 2005 Ford Econoline, 2005 Ford E450 Super Duty, and 2005 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
The driveshaft coupling that allows length changes to occur while the suspension articulates and while the driveshaft rotates.