Saturday-night special

Meanings

1. An inexpensive, easily obtained handgun.
2. An overnight weekend train.
3. A seasonal (usually October to December) sale on Saturday evening.
4. A girl who can be dated easily on Saturday evenings.
5. An unexpected takeover bid that gives its opponents little time to respond.

Etymology

Attested from 1917, akin to Saturday-night pistol attested from 1915. Not entirely clear, but perhaps from phrases like “Saturday night pistol slaying” and “Saturday night pistol scrape” often found in early 20th century local crime reporting due to the fact that Saturday evening had been the peak time for homicides and similar crimes. Also likely to be enforced by the obsolete meaning of a cheap sale and usage of "Special" in the context of more powerful firearms like Colt Police Positive Special.