Meaning

noun poisonous perennial Old World vine having violet flowers and oval coral-red berries; widespread weed in North America

noun twining shrub of North America having yellow capsules enclosing scarlet seeds

adjective tinged with sadness

originFrom Middle English bitterswete, biterswete, equivalent to bitter + sweet. Cognate with Saterland Frisian bitterswäit (“bittersweet”), West Frisian bittersoet (“bittersweet”), Dutch bitterzoet (“bittersweet”), German bittersüß (“bittersweet”), Danish bittersød (“bittersweet”), Swedish bittersöt (“bittersweet”).

Etymology from Wiktionary, CC BY-SA 3.0