Muffin Top

Muffin Top \MUHF-in-TOP\ , noun;
1. A crisp, flat muffin that resembles the top portion of a typical muffin
2. Slang: A roll of excess fat that hangs out over a person's waist when wearing a garment with a tight waistband

Never a good look... (source)

The word muffin dates to 1703 and originally was spelled moofin. It is possibly derived from Low German muffen, the plural of muffe ("small cake"). It may also be connected with Old French moufflet, which was an adjective for bread that meant "soft."
Muffin top, specifically, is first attested in 1914 in reference to the top of an actual muffin. The slang term, depicted above, is not recorded until 2003. Perhaps it is no accident that back in 2003 low-waisted jeans and midriff-baring shirts were, unfortunately, in style at the same time.