Trousers.A third guy wandered in wearing an old pair of trackie daks (with a hole in one knee) and a tatty old jumper....
An old grey-haired but balding man approaches, wearing trackie daks.
A bronzed lifesaver in bright red pool daks and a goofy cap is an Australian icon, although they're starting to wear shorts a la Baywatch or bikepants lately.
Origin
1930s (as a proprietary name for a brand of clothing): first recorded in this sense in the 1970s.