If you plan on going to USA: A change up is a deceptively slow pitch intended to throw off the batter's timing. (Sport of baseball) Otherwise, go with the answer by Bob.

Isabel, it's a very good question! Thank you, Bob. It makes a lot of sense.

Thank you very much Bob.

Hello Isabel, Change is a process where something does not remain constant. So a boy changes into a man. If you change up you are either moving from one gear to another when driving or sometimes it can mean that you are improving your situation. Hope this helps Bob