half a sacrifice, ribs, abundant, plentiful
胖 centers on physical abundance and fleshiness: plentifulness, ribs as a meaty part, and by extension a sacrificial half-animal. The meanings connect through the idea of a substantial, fleshy offering.
胖 combines ⺼ (flesh/meat) with 半, which likely contributes the sound and the idea of a half or portion. The character originally referred to a half-carcass used in sacrifices, hence the connection to ribs and abundance.
The flesh radical ⺼ beside 半 (half) suggests a half-side of meat, like a rib section. Picture a butcher presenting a generous, fleshy half-carcass: it's abundant and plentiful.
For ハン, imagine a hand (ハン sounds like 'hand') holding a half-portion of ribs: hand -> ハン, and the hand offers the abundant meat.