Is 'ugg' a brand name or a generic term used to describe sheepskin footwear?

The answer to this question depends on your location.

In Australia ugg boots is not a brand name, it’s a generic term that has been used for decades to describe sheepskin footwear.

Outside of Australia, an American company called Deckers Outdoor Corporation has trademarked terms ‘ugg’ and ‘ugg Australia’ and holds the exclusive rights to those terms. Meaning that outside Australia, ‘ugg’ is a brand and ugg boots are a product made by Deckers Outdoor Corporation.