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Labour of Sisyphus: King Sisyphus, a noted ancient Greek trickster, was made to roll a huge boulder up a steep hill, but before he could reach the summit, the rock always rolled back down, and he had to begin again. The exasperating nature of this punishment was visited on King Sisyphus because of his arrogant belief that his cleverness surpassed that of Zeus. The king of the gods, Zeus, therefore demonstrated his own cleverness by forcing Sisyphus to labour for eternity at this pointless task.
It's an interesting illustration of the ancient Greek's attitude to deities and might even explain to some extent the peculiar attitude held by some modern religious groups about the nature of their particular gods.
As a result of this myth, pointless or interminable tasks are often described as Sisyphean.
'When Julie announced her determination to turn her four acres of wilderness into a modern garden with not a weed in sight, Terrence laughed and told her she'd set herself a Labour of Sisyphus.'