What's the significance of this ornament? A girl gave it to me.

Congratulations on your good luck.

This is a pair of little dolphin ornaments. Dolphin products are generally named "dolphin love" because there are allusions here. The following is a short online version of this story:

"A long time ago, Son of God violated the taboo of the celestial world and fell in love with the girl on earth, and was not allowed to be in the celestial world and the mortal world. They have traveled all over the world, but they can't find a place to live. Only the fairy queen, who lives in the deepest part of the forest, sympathized with their situation and gave the couple a pair of spiritual bronze rings to protect them from crossing the sea safely. However, the jealous God discovered the secret of the copper ring and threw it into the sea, so the lovers who lost the protection of the copper ring were washed away by the big waves. Even so, they searched for each other wholeheartedly until the last moment.

Dawn is approaching, and the two are about to go up in smoke. This love touched the kind dolphin and jumped out of the sea with a bronze ring in her mouth at dawn, so that the couple regained the blessing of the elf queen and stayed together for a long time. When the first light shone on the white beach, the whole beach turned into a happy pink, and dolphins became the patron saint of love from then on. Legend has it that as long as you sincerely pray for dolphins, the expected love will come true. "

Double dolphins mean in pairs.

I hope to have some reference.

Good luck!