From Sima Xiangru's Han-dynasty 《上林赋》: 沸乎暴怒，汹涌澎湃 — describing a violently churning river. Originally literal water imagery, extended to any overwhelming force.
usage
Often applied metaphorically to emotions (激情, 热情), movements (革命, 浪潮), or music. Implies grandeur and unstoppability, not just volume.
