nest egg

noun

money saved and held in reserve for emergencies, retirement, etc.

a natural or artificial egg placed in a nest to induce a hen to continue laying eggs there.

Origin

1600-10

Examples from the web for nest egg

Nor was it money, even though he is sitting on a shrinking nest egg.
Yet that is exactly what you do when you put money into a retirement nest egg.
In other words, if your money is not earning more than the rate of inflation, you will lose part of your nest egg's buying power.
Develop a savings plan to create a nest egg for your retirement.
Bottom line, however is that there is no investment that can turn a nearly empty nest egg into a full one.
But you are responsible for building up a nest egg big enough to support yourself, and perhaps your family, in retirement.
With a smaller nest egg, older workers may thus have decided that they cannot yet afford to retire.

British Dictionary definitions for nest egg

noun

a fund of money kept in reserve; savings

a natural or artificial egg left in a nest to induce hens to lay their eggs in it

Slang definitions & phrases for nest egg

noun phrase

Saved money, esp for use in retirement or an enterprise, emergency, etc (1700+)