It also acts as an unseen block to promotion. A private who's spent most of his army career (whether a set timespan or duration of hostilities) on 'jankers' would be most unlikely to ever make it above Private because he is obviously untrustworthy and incapable of taking orders. One of the best known 'jankers' punishments was weeding the parade ground by hand, or with a dessert spoon. Painting rocks white was also another unpopular task, as was digging latrines. I've seen reports in a military diary that had half a battalion painting rocks white and the other half painting them brown again (the crime was a practical joke involving drawers cellular,no one culprit could be found, so the entire battalion were punished). It was usuallly dirty, unpopular jobs - spud bashing, mopping down floors, mucking out stables or clearing latrines: or "busy work" - tedious, unnecessary and soul destroying stuff, meant to break the spirit of anyone kicking against the system. For a movie example (albeit an extreme one), watch Sean Connery in 'The Hill'. It's a prime example of a pointless and demeaning excercise, serving only to break the man. Plus it shows Sean with his clothes off.

I've a feeling the actual word has it's roots in one of the Asian languages, probably Hindi, as it would have been popularised by the British Army in India during the 1800's.

LTS