Most fans already know where C-3PO came from. Anakin built him from spare parts on Tatooine when he was still a little kid, mainly to help his mother, Shmi.
But the “three” in C-3PO’s name had a more personal meaning. In The Phantom Menace novelization, Anakin saw Threepio as the third member of his little family: Shmi, himself, and the droid.
Anakin Saw C-3PO as a Family Member
We usually remember the simple reason Anakin built C-3PO: he wanted a protocol droid to help his mother, Shmi.
That is true, but it was not the only reason Threepio mattered to him. In Matthew Stover’s Revenge of the Sith novelization, Anakin later tells Padmé, “I didn’t have many friends when I was a kid, so I built one.”
But for Anakin, C-3PO was not simply a friend or just a droid built to help his mother. Anakin felt that C-3PO was a member of his small family on Tatooine.
In Terry Brooks’ The Phantom Menace novelization, there is a detail that when Anakin was in the final stages of finishing C-3PO, he added the number three to the droid’s name to represent that this protocol droid was the third member of his little Skywalker family.
Shmi Completed What Anakin Started
According to the Attack of the Clones novelization, C-3PO was finally completed by Shmi Skywalker.
When Anakin left Tatooine with the Jedi, Threepio was already functional, but his outer coverings were still missing. His wires and internal parts remained exposed, just as we see him in The Phantom Menace.
Shmi kept him that way for a long time because part of her still hoped Anakin might come back and finish the droid himself.
That changed before she married Cliegg Lars. The novel explains that Shmi finally added C-3PO’s dull metal coverings on her own, completing the droid Anakin had left behind.
For Shmi, finishing Threepio meant accepting that Anakin now had another life away from Tatooine, just as she was about to begin a new life of her own.
