Words use arises from an oddly named and still standing 18th century mill in the Town of Dewsbury in West Yorkshire, UK. Shoddy & Mungo Ltd. This mill used to be involved with 'Worsted' this is the cheapest and worst to deal with hence its name form of woollen product. The name shoddy was forever more connected with the worst of the industries business.
Locally and Nationally people also use it as a way of describing ones state when one is high from smoking biftas
"that is just shoddy workmanship"
"I am feeling a bit shoddy"