noun
sweeping over; engulfing
Describes a natural force or disaster that sweeps over a wide area, leaving nothing untouched. Often used with 津波, 洪水, 火災, etc.
津波が沿岸の町を総なめにした。
The tsunami swept over the coastal town.
noun
Used in competitive contexts (sports, elections, awards) when one side wins everything or takes all prizes.
彼の作品が賞を総なめにした。
His work made a clean sweep of the awards.
席巻 also means sweeping or dominating, but emphasizes overwhelming force or popularity, often in a figurative sense (e.g., a trend sweeping society). 総なめ is more concrete, implying that nothing is left behind.
Compound of 総 (all, whole) and 嘗め (from 嘗める, to lick or taste, here metaphorically meaning to sweep over or engulf). The image is of something licking up everything in its path.