贩

Left shell radical, simplified from 貝 — the cowrie shell that served as early currency. It indexes 贩 in the money-and-trade family: 买 buy, 卖 sell, 货 goods, 贵 expensive. A 贩 is a peddler or small-trader, and the shell on the left marks every transaction they handle.

Right side 反 supplies the sound directly: fǎn drifting to fàn with the regular tone shift. Same phonetic powers 饭 rice, 板 plank, 版 edition, 返 return. Faint semantic flavor too: a peddler 'turns over' goods — buys and resells, flips inventory — exactly the 'to flip' core meaning of 反. The merchant is, literally, in the business of reversal.