Either he worked for a butcher called "Laviage" - as I can only find this as a name
or lavage - as you suggest, phillipsearching - means
A washing, especially of a hollow organ, such as the stomach or lower bowel, with repeated injections of water.
He cleaned the tripes!
My mum loves tripe and onions! (Yeugghh)
Watermusic
By the way another one found this week Hemp Draper The draper meaning dealer in dry goods - he was a buyer of hemp for the rope industry.