Definition & Meaning of "[put] on an act"

What is the origin of the idiom "put on an act" and when to use it?

The idiom "put on an act" originated from the world of theater, where actors would wear costumes and assume roles to portray fictional characters on stage. The phrase signifies the deliberate act of pretending or feigning a particular behavior, emotion, or persona to deceive or manipulate others and is commonly used to describe situations where someone intentionally behaves in a manner inconsistent with their genuine feelings or intentions, often for the purpose of gaining an advantage or masking their true motives.