Emily Dickinson Lexicon

DUG, n. [Ice. deggia. This word corresponds with the root of L. digitus, Eng. toe, Norm. doy, a finger, signifying a shoot or point.]

The pap or nipple of a cow or other beast. It is applied to a human female in contempt, but it seems to have been used formerly of the human breast without reproach. From tender dug of common nurse. – Spenser.