To hide or store something in a safe place, especially for future use, like how a squirrel hides nuts.
Squirrelled can make people think of being sneaky or clever, like a squirrel hiding nuts.
Examples:
She squirrelled away her favorite toys in a secret place.
He squirrelled his candy in his backpack.
The squirrel squirrelled away all the nuts for the winter.
I squirrelled my snacks in my room so my brother wouldn't find them.
She squirrelled away so much money that she could buy a big present.
The squirrel squirrelled away so many nuts that it had no room left in its house.