Kowtow, which describes the act of kneeling and touching one’s head to the ground to show respect, used to be a custom in Chinese culture. Now it refers to acting like you're doing that, whether you actually bow or not.
Kowtow is derived from the Chinese word k’o-t’ou, which literally means “knock the head.” As a verb, kowtow has the sense of “sucking up” or "flattering." Maybe you’re wondering when it would be appropriate to kowtow. The answer? When you want to worship, show respect, gain favor, or flatter. You might need to kowtow to your teacher if you failed a test, but if you kowtow to all your neighbor's requests, you might wind up mowing his lawn all summer.