Definition: Confused, entangled or embarrassed.
Origin
Pig Players gave just about every creature that can bend its body into a round little ball the credit for the creation of this expression. But, alas, the origin has nothing to do with an animal’s ability to turn itself into a comma. It has to do, surprisingly, with balls — snowballs, that is. Traced to about 1880, “all balled up” referred to the state of horses’ feet after walking in soft winter snow. Forming packed ice balls on a horse’s hooves, needless to say, can make walking difficult and frequently horses found themselves nose first in a snow drift. Quite embarrassing, I’m sure. High fives to the only two people to come up with the answer: Lin_Duh and Nawojcik.
