So maybe, or maybe not, Caleb was the father?
Or maybe nothing was further from Calebs mind, but they had a rellie, also with surname Measures, who was visiting at some point and did not have such pure morals as Caleb may (or may not) have done?
Or maybe the Measures were very good supportive friends and neighbours of Eliza's at a difficult time, maybe chosen as godparents, so she called her daughter after them.
We will never know.