More on the wrists of Molly: When Drummle shows how muscular his arm is and the other young men "fell to baring and spanning our arms in a ridiculous manner," Mr. Jaggers suddenly claps "his large hand on the housekeeper's like a trap" as she reaches across the table. "If you talk of strength," said Mr. Jaggers, "I'll show you a wrist...."
Jaggers shows the young men a wrist deeply scarred, telling them "There's power here." He explains that she has a wrist stronger than most men; the hands have a great "force of grip," as well.
Later in the novel, Pip learns what these remarkable wrists have done.
In Ch.26 Pip meets Molly, Jaggers' housekeeper, for the first time when he is invited for dinner at Jaggers' house alongwith his friends. On seeing her for the first time, he is struck by the resemblance of her face to the face of another person with whom he is familiar, but somehow he is not able to make the connection just then. Pip has seen a performance of Shakespeare's Macbeth and the housekeeper's face reminded him of the face that rises out of the witches' cauldron in the play: "I always saw in her face, a face rising out of the caldron." Pip also has an opportunity to examine Molly's wrists closely when Jaggers asks Molly to show them her wrists: "Molly let them see both your wrists."
The link ofcourse is, that the housekeeper Molly is no one else but Estella's mother. Its only much later in Ch.48 that he makes the connection between Estella and Molly. In Ch.44 he observes very closely Estella's hand as she's knitting and in Ch.48 he observes very closely Molly as she serves him food and he is convinced that Molly is certainly Estella's mother: "And I felt absolutely certain that this woman was Estella's mother."