Q:

Why do native speakers use "vent your anger" rather than "erase your anger"?

Today, I learnt a new phrase: 

vent your anger

That means calm someone down.
But I am confused because the word erase also means make something disappear, so I am wondering if the word vent could be replaced by the word erase?

A:

I'm afraid the meaning you were given is not what most people understand by it. Merriam-Webster gives me this definition for vent:

to express (an emotion) usually in a loud or angry manner

When you vent your anger, it is not so much about making the anger disappear, but about letting it out.
I've not often heard about someone erasing their anger, but I would imagine, that they count to ten, and decide not to become visibly, noticeably angry.
Someone who vents his anger will actually shout, swear, hit someone, or whatever else they decide to do to actually show their anger.
They assumption is that after venting one's anger, the anger is less, or completely gone, but the act of venting it is actually showing one's anger.

