Possibly from the opening scene of Monty Python's Life of Brian (1979). Shepherds are discussing sheep and the topic strays to cats: "Can you imagine a herds of cats waiting to be sheared? Meow! Meow! Woo hoo hoo."
- (idiomatic, in similes) To attempt to control the uncontrollable.
- Managing volunteers from fourteen different organizations is like herding cats.