付け加える
つけくわえる · tsukekuwaeru · JLPT N1 · verb-ichidan
to add one thing to another
付 — person radical 亻 + hand 寸
付 originally pictured a hand (寸) reaching out to hand something to a person (亻), depicting the act of giving or delivering. The core sense 'to hand over, deliver, pay' has remained stable since ancient bronze inscriptions. It also serves as a phonetic component in characters like 附, 符, and 府.
加 — force 力 + mouth 口
加 is traditionally analyzed as a compound of 力 (strength) and 口 (mouth), suggesting boasting or exaggerating one's effort with words. From this it extended to the meaning 'to add' or 'increase'. Today it is used broadly for addition, both literal and figurative.