Sarah Bush Johnston photograph

[RJNorton]

Reference to Sarah Bush Johnston Lincoln being called "Sally" is even in Herndon's Informants. For example, in an August 1, 1865, letter from John B. Helm to William Herndon it says:

"It is also plain that old Tom Lincoln had courted Sally Bush before she married Johnson and failed to get her — that Sally Bush and Johnson had had a number of children...It also appears that not long after this Sally Bush then the widdow Johnson was lawfully married to Tom Lincoln and Abe was received into her family as a step son — This is a new era in Abe Lincolns life."

IMO, using the nickname of Sally for Sarah was common. I have also seen reference to Sarah Lincoln Grigsby, Abraham's sister, being called Sally.