Awkward emotionally, she was named Santal by Malthar, an archmage of Waterdeep specializing in golemcraft. For many years, Santal served Malthar with her "brother", a powerful juggernaut named Wrath. They were both convinced that Malthar had created them, shaping Santal from wood of the same name in the shape of a woman, as a companion.
One day when Malthar was away, Wrath rebelled and wrecked their laboratory then left through a magical gate. Santal, curious and scared, went after Wrath but was too late and never found him again. What she found was the strange streets of Waterdeep, where an orphan helped her. Thus, Santal had met BB.
Santal earned her nickname from her proficiency with magic, and because she rebuilt herself with metal plates when she learned the skills of an Artificer.