buy a pig in a poke

To buy something without inspecting it thoroughly, often with negative consequences. The phrase refers to a confidence trick in which people would buy what they thought was a pig in a bag (or "poke") and later found that the bag actually contained a cat. Purchasing a home without inspecting it first is like buying a pig in a poke. Only a fool would buy a car sight unseen. You might as well buy a pig in a poke! Turns out Joe bought a pig in a poke from that shady jeweler. The stone is far from a real diamond.

Fig. to buy something without looking inside first. If you don't get a good look at the engine of a used car before you buy it, you'll wind up buying a pig in a poke. I just took the salesman's word that this camera worked. I guess I bought a pig in a poke.

To purchase something sight unseen and risk disappointment. The term comes from the ancient dishonest practice of putting a worthless cat in a bag (poke) in place of a young suckling pig, an expensive delicacy. The term was proverbial by the time John Heywood collected his proverbs (1546) and has been used ever since. See also let the cat out of the bag.