'I was solomnly told that 'tyum uns' was a dialect work meaning empty tubs in a coal mine.
It is simply misheard t'empty uns, the empty ones.' Rum'n'coke

Not sure that is right — there is a Scottish & Northern English dialect word 'toom' which means 'empty' — remember the line in the Bonny James/George Campbell ballad [Child#210] - "Toom was the saddle sae bloody to see When hame came his good horse but never came he".