Often spelt as Toe Rag or toerag.
Originally was Tow Rag from the red rag tied to the end of a truck carrying a long load (in England) or the rag tied to the rope towing another vehicle so people would not decapitate themselves by going through the gap.
Pretty well the rear end of everything and of no other use.
(Being poilte here)
"you useless tow rag"
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