A poke has the same origins as pocket and pouch and is a small bag within which a young pig could be packaged after being sold at a farmers’ market.
In 1540 it was recorded that unscrupulous farmers would sometimes replace the pig with a cat and advise purchasers not to open the bag until they reached home or the pig might escape.
If the poke was opened, the cat was out of the bag, and the seller had been caught cheating.