What is the Origin of fly-by-night?

The term "fly-by-night" originates from the 19th-century practice of fly-by-night businesses, which often operated without a permanent location and were known for being unreliable or dishonest. These businesses would appear quickly and disappear just as swiftly, leaving customers dissatisfied. The phrase implies a lack of stability and trustworthiness, often associated with people or companies that take advantage of others for quick gains. Its usage has since expanded to describe any unreliable or transient person or operation.