The Draupnir ring was an inexhaustible source of wealth: every nine nights, eight more rings would come out of it, all identical (except for their inability to produce more of the same). Thus, Draupnir means "the dripping" because of its ability to make other rings "drip" from it. It was forged by two dwarves, Brokk and Eitri.
Odin placed it on the funeral pyre of his son Baldr. According to two of the four main manuscripts of the Edda of Snorri (the Codex Regius and the Codex Wormianus), it is only after this that it acquired the property to reproduce itself identically.
The ring, in general, is in the Germanic world a symbol of sovereignty, and this one can be seen as a way for Odin to manifest his power to the goddess of the dead Hel.
Draupnir was then recovered by Hermod, Baldr's brother. Afterwards, Freyr asked Skirnir, his servant, to give it to the giantess Gerd as a token of his love. This is told in the Skirnismal.