Doing something is like herding cats refers to any activity which is extremely difficult and quite possibly futile, suggesting there are wildly unpredictable forces at play. It’s most often used when referring to managing a given group of people, especially programmers, or managing a software project.
The Washington Post Magazine of 9 June 1985 is often quoted as the earliest use in print:
At Group L, Stoffel oversees six first-rate programmers, a managerial challenge roughly comparable to herding cats.
Warren Bennis’s book Managing People Is Like Herding Cats helped to popularise the term herding cats. He said “Be humble. Stop trying to herd cats and start building trust and mutual respect. Your cats will respond. They will sense your purpose, keep your business purring, and even kill your rats.”
Herding Cats (or Cat Herders) is a popular advertisement that is often used to illustrate the complexity of managing business change.