The word "姊姊" is formed by reduplicating the character "姊", which is itself a pictophonetic character composed of the semantic radical "女" (female) indicating its meaning related to women, and the phonetic component "𠂔" (zǐ) providing its approximate pronunciation. This repetition results in a term specifically denoting "older sister", with the duplicated structure emphasizing familiarity or affectionate address in usage.