The word "热门" is formed by combining the character "热" (rè), meaning "hot", with "门" (mén), meaning "door" or "gate". Here, "门" is used figuratively to represent a field, category, or area of interest. Together, they create a compound where "热" conveys intensity or widespread attention, and "门" denotes the specific domain, resulting in the meaning of "popular" or "trending" within that context.