If you have stashed something, you have hidden it in a secret place.
Stashing something can make people think of secrets, surprises, or sneaky things.
Examples:
He stashed the treasure under the bed.
She stashed the cookies in the cupboard.
The squirrel stashed nuts in the tree.
I stashed my toys in the closet so my brother wouldn't find them.
She stashed her diary in a secret hiding place.
The pirate stashed his gold on a desert island.