No room to swing a cat

During the whipping punishment using the ‘cat o’ nine tails,’ all hands were called on deck to witness. With a full crew, the deck could be so crowded that the cat o’ nine tails was difficult to use without hitting other crew members. In other words, there was ‘no room to swing a cat.’ Today the expression is used to indicate crowded or packed surroundings. A nautical term that has now become part of everyday language