Meaning

noun East Indian tree bearing a profusion of intense vermilion velvet-textured blooms and yielding a yellow dye

originFrom DAKS, trademark for a brand of trousers originally made in the 1930s by Simpsons of Piccadilly created by Alexander Simpson and his business partner Dudley Beck. Blend of dad + slacks, named after Simeon Simpson, the founder of the company and the American word for informal trousers.

Etymology from Wiktionary, CC BY-SA 3.0