Colloquially speaking, "to push somebody's buttons" means to irritate or annoy the person. And, "know what buttons to push" means to know what to do to get people to act the way you want.
I can't understand how come "buttons" are associated with people and their behavior. How did these idioms come to be?
Edit: I feel I am not being clear with the question. What I intend to understand is the relation of a person's pysch and buttons. As it is unusual to talk of hurting a machine's feeling, likewise it should be unusual to speak of somebody's button as well. This being my point, how did the metaphorical idiom originate(and considered meaningful)?
Best Answer
It's a metaphorical usage, so there doesn't have to be a direct link between people and pushing the buttons they don't have.
Dictionary.com indicates the phrase originated in 1920s America, when domestic electricity was being installed on a massive scale. The ability to push a button to turn something on had a big impact on lifestyle, and the metaphor spilled over into other things which have an immediate effect — like being able to trigger a specific emotion.