The word 私家 is formed by directly combining two fundamental concepts: 私 (sī), meaning "private" or "personal", and 家 (jiā), meaning "household", "family", or "home". The formation conceptually merges these ideas to denote something that belongs to or is for the private sphere of an individual or family, as opposed to the public or official domain. It effectively creates a compound idea of "privately-owned" or "for personal/family use", which is then applied to various nouns (like 私家车, private car) to specify this exclusive, non-public nature.