The word "明明" is formed by the reduplication of the character "明", which itself is a compound ideograph composed of the radicals "日" (sun) and "月" (moon) to denote brightness or clarity. This duplication creates an adverb that intensifies the original meaning, resulting in a term used to emphasize something as being obvious or unequivocal, such as in "明明知道" (clearly know). The formation is a straightforward instance of character repetition for semantic emphasis.