壮大
そうだい · soudai · JLPT N1 · na-adj
magnificent
壮 — 爿 (bed/plank, phonetic) + 士 (scholar/warrior)
A semantic-phonetic compound. 士 ('warrior, man') gives the meaning of strength and vigor, while 爿 ('plank, bed') supplies the sound. Originally describing a robust, sturdy man, it broadened to mean 'strong, robust, magnificent' in general.
大 — pictograph of a person with arms outstretched
大 is a pictograph showing a person standing with arms and legs spread wide. The outstretched arms suggest 'big' or 'great', extending from the literal image of a large stance to abstract meanings like important or grand. It is one of the oldest characters, found on oracle bones.