Chekhov's gun

Meanings

1. A dramatic principle that states that every element in a story must be necessary, and irrelevant elements should be removed.
2. An element that is introduced early in the story whose significance to the plot does not become clear until later.

Etymology

Calque of Russian Чеховское ружьё (Čexovskoje ružʹjó). The principle was articulated by Russian playwright Anton Chekhov and reported in various forms.