The name back-end loader or a rear-end loader (as opposed to a front-end loader) or just a rear loader (as opposed to front loader) seems fine. 
 Back in the day all the construction, material handling, agricultural, etc equipment was based on the simple tractor design. And if you think about it, it's just a tractor with the arm and bucket contraption attached to its back (as opposed to attaching the arm and bucket to the tractor's front). The first rough terrain / agrucultural forklift trucks were made in the same way, a post and forks contraption attached to the tractor's back.