At the end of Nalo Hopkinson's novel Midnight Robber (2000), Tan-Tan, the main character, gives birth to a boy. Her friend Melonhead asks how she will name him:

"Tubman." Tan-Tan surprised herself, coming out with it so quickly. She hadn't been thinking about what to call him. She smiled up at Melonhead.

Why does Tan-Tan choose the name Tubman?