Derived from Greek ἀμαρύσσω (amarysso) meaning “to sparkle”. This was the name of a heroine in Virgil’s epic poem Eclogues [1]. The amaryllis flower is named for her.
Possibly from the Germanic name Adelmar, maybe influenced by Latin amarus “bitter”. This was the name of a legendary saint who was said to have sailed across the Atlantic to a paradise. He is especially popular in Galicia and Asturias in Spain.