I swear we didn't teach it to him...

Yesterday while watching our cartoons in the morning there was a donkey on screen and Nick pointed to it and said "ass". Hmmm...we didn't teach him this, so where did he learn it?

Fast forward to today....we're watching the Wiggles this morning and there is a horse on screen. He points to it and says "ass".

Does anyone know who's been teaching my son this?