The word "熟悉" is formed through the semantic combination of its two constituent characters. The first character, "熟", originally conveys the ideas of ripeness, thorough cooking, or maturation, metaphorically extending to mean "familiar" or "well-acquainted". The second character, "悉", means "to know in detail" or "to be entirely aware". Together, they compound to create a single concept where "熟" provides the qualitative state of deep familiarity and "悉" adds the aspect of comprehensive knowledge, resulting in the integrated meaning of being thoroughly acquainted with or knowledgeable about someone or something.