Question

What litarary device is this when someone says "He keeps his trap shut"

Answer 1

The phrase "He keeps his trap shut" employs **idiom** as a literary device. An idiom is a common expression whose meaning is not deducible from the literal definitions of its individual words. In this case, "trap" refers to the mouth, and the phrase means that someone is remaining silent or not speaking. Additionally, there could be elements of **colloquialism**, as the phrase uses informal language typical of everyday speech.