Someone described as being the “king of the castle” is in an extremely advantageous position of comfort and well-being. The phrase is an English idiom which usually refers to someone who has a position of power within a larger group. It can also refer to someone who is in complete control of a situation and seems to have no problems at all maintaining that position. “King of the castle” is one of many idioms that play off the power of kings in the period of time before they mostly became figureheads without any significant power.
The distinguishing characteristic of an idiom is the fact that it may have a meaning which, though completely understood by the people within a specific culture, might not coincide with the literal definitions of the words it contains. Most idioms are phrases of just a few words and they take their meanings from popular usage over time. Those meanings often evolve from what their originally usage might have intended. Idioms also provide color and impact to conversational English. One idiom describing someone in a position of power is the expression “king of the castle.”
A person who is described in this manner holds some sort of authority and leverage over others in his or her proximity. It can be because the person has always had this power, or it could be a position to which the person in question has ascended. In any case, it is a position that often begets envy and admiration from others. As an example, someone might say, “In that little social group, he is definitely the king of the castle in terms of how he orders them around.”
This phrase can also be used if a person simply has control over a situation. It can be used describing someone who has a position of comfort in his or her work environment. The phrase can also depict someone in an advantageous spot in their personal life. For example, consider the sentence, “I am truly king of the castle when it comes to the way my family treats me.”
Although they have lost some of their authority in modern times, kings were once the most powerful figures in the world. A king could basically have almost anything he wished or desired. It is the hint of that kind of power which gives the phrase “king of the castle” its distinctive impact.