Adah: the first of Lamech's two wives in the line of Cain, and the mother of Jabal and Jubal.
Genesis 4 follows the family of Cain down to Lamech, who took two wives. Adah is named first and Zillah (צִלָּה) second. This is the first time the Bible reports a man with more than one wife, and it comes at the close of a family line already marked by murder.
Adah is the mother of two of the sons Genesis credits with starting a whole way of living. Jabal, her firstborn, is remembered as the first to live in tents and keep herds, and his brother Jubal as the first to play the harp and the pipe. Their half brother Tubal-cain, born to Zillah, works bronze and iron. Between the two women, this one household is given the beginnings of herding, music, and metalwork.
Her name is written exactly like the everyday Hebrew word for putting on jewelry, and it is usually taken as a form of the word for the finery itself (עֲדִי), which is why it is often glossed "Ornament". Genesis never explains the name, so that reading stays a careful reconstruction rather than something the text says.
The last thing Genesis reports of her is that she was spoken to. Lamech gathers his two wives and recites a short, savage boast about killing a man who wounded him. It is the oldest piece of poetry in the book, and Adah is half its audience.