지족(知足) means "contentment," but when I first saw the Chinese characters for this word, I could not understand how "contentment" could be achieved by "knowing one's foot" (知 means "know," and 足 means "foot"). After doing a little research, however, I found that besides meaning "foot," 足(족) can also mean "enough," "sufficient," or "plenty." Therefore, 지족(知足)하다 literally means, "know enough."
It seems that people can find contentment when they know their place in life and are satisfied with what they have.
Of course, none of this explains why the Chinese character for "foot" is also used to mean "enough"?