Right
乏 supplies the sound — fá shifted to fàn, only tone differs.
乏 itself originally pictured a shield with crossed planks for 'depleted, lacking' (the upside-down
正); the meaning doesn't carry. Pure phonetic. The water-with-
乏 pairing also gives
贬 (depreciate, demote) via
贝-radical and
砭 (stone needle) via
石-radical — the right side a stable phonetic across that small family.