The word "不知不觉" is formed by combining two negative verb phrases: "不知" meaning "not know" and "不觉" meaning "not feel", with each phrase using the negation "不" before a verb related to awareness. The repetition of "不" reinforces the negation, and the juxtaposition of the synonyms "知" and "觉" creates a compound that literally means "not knowing and not feeling", conveying the sense of something occurring without conscious perception.