The word "婆婆" is formed by reduplicating the character "婆", which itself is a phono-semantic compound consisting of the semantic component "女" meaning "woman" and the phonetic component "波" providing approximate pronunciation. This duplication creates a disyllabic word that specifically refers to "husband's mother" or "mother-in-law", with the repeated character narrowing the meaning from a general elderly woman to a precise familial relation.