Any excuse for getting out of work, an obligation or promise. Sometimes thought to be a sexual euphemism, but not. A reason to be lazy.
A. Boss: Can you stay late this evening, we have to ship twenty more units before 5pm?
Employee: Sorry, boss, but I have to get home as soon as I can to clean the hamster cage!
B. Person 1: Can I get that money back that you borrowed last week?
Person 2: Sorry, but I have to get home as soon as possible to clean the hamster cage!