In the late 900's France, when royalty would have large drinking garden parties, the manor would be too far away to relieve themselves so young/simple boys would carry small buckets, ready for the call for them to 'assist'.
So, a simple pissboy
"come here pissboy, I must relieve myself."
" You wouldn't make a pissboy in your finest hour"
" Hey, pissboy, why don't you clean the bucket and get my shoes."