rumpsocks 

Socks for your rump.

Geez! Look at these nifty rumpsocks I bought for my bum!

rumpsocks by Alina Naomi May 23, 2007

Rumpsack 

to land ones ass (rump) on ones testicles (sack) in a painful manner.

Robert: Ahhhh that hurts so much
Harriet: What did you do? you only sat down...
Robert: No i Rumpsacked!!

Rumpsack by RobertnHarriet August 11, 2011