wire cap; terminal cover
Specifically refers to a small insulating cap placed over the end of a wire or terminal. Common in electrical work.
After wiring, please attach a terminal cover to the terminal.
The cable sheath is damaged, so it needs to be replaced.
The sheath of this machine has excellent heat resistance.
sheathed heater
sheath silhouette
Borrowed from English 'sheath'. The specific electrical sense 'wire cap' is a semantic extension in Japanese technical usage.