Duty Free

Like when your family goes out of town without you and you have the house all to yourself, with no chores. You're completely free of duties.

In the financial world, it has to do with getting something without having to pay taxes on it. Or at least not having to pay certain taxes.

You'll usually find "duty free stores" in border areas between countries, or at certain international airports. The general idea is that you can purchase things (alcohol and perfume are stereotypical duty-free items) without having to pay the going taxes for a particular country. Under highly Protectionist laws in Europe, duties or taxes were a huge part of the purchase of things like cigars and champagne and perfume.

Over time, American-made competition bit into the competitive powers of those countries and, well, the value of being "duty free" was diminished. There is a whole chain of Duty Free shops which, in fact, sell mostly products that are duty free...everywhere. It's just that the "semi-on-sale" notion of that un-duty'd discount made those items be perceived as a bargain to myriad buyers with their last vestiges of foreign currency to spend on keepsakes and crapsakes.