An heirloom is something special. The true definition is a piece of property that descends to the heir as an inseparable part of an inheritance of real property and/or something of special value handed on from one generation to another.
You may have your mothers wedding dress but have it redesigned for your own wedding. Left overs of the dress can be used for sachets, pillows, doll clothes, etc. It is a way to keep a memory going with a cherished item.