Merriam-Webster Online Dictionary
heirloom (noun)1.
a piece of property that descends to the heir as an inseparable part of an inheritance of real property
2.
something of special value handed on from one generation to another
3.
a horticultural variety that has survived for several generations usually due to the efforts of private individuals
heirloom (Wikipedia)
In popular usage, an heirloom is something that has been passed down for generations through family members. Examples are a Family Bible, antiques, weapons or jewelry.
The term originated with the historical principle of an heirloom in English law, a chattel which by immemorial usage was regarded as annexed by inheritance to a family estate. Loom originally meant a tool. Such genuine heirlooms were almost unknown by the beginning of the twentieth century.