怕

Left-side heart radical - the indexing radical, side-form of 心. Files 怕 in the family of emotion/feeling verbs: 怒 (anger), 怀 (cherish), 恨 (hate), 慢 (slow-tempered), 情 (emotion). Marks fear as a matter of the heart, which is exactly how classical Chinese psychology categorized it.

Right-side 白 supplies the sound - bái shifting to pà in 怕 (b/p alternation common to this phonetic series). 白 also adds a beautifully apt semantic flavor: 'heart turning pale white' is the universal physical sign of fear - drained blood from the face. Mnemonic and etymology align. Phonetic family: 拍 (clap), 泊 (anchor), 伯 (uncle), 柏 (cypress).