C. Used interjectionally. Dear!, Oh dear!, Dear, dear!, Dear me!: exclamations expressing surprise, astonishment, anxiety, distress, regret, sympathy, or other emotion. dear bless, help, love, save us (you): ejaculations of astonishment, usually implying an appeal for higher help (obs. or dial.). dear knows! goodness knows, Heaven knows (I do not).
These uses with a verb suggest that dear represents or implies a fuller dear Lord! Thus dear knows! is exactly equivalent to the Lord or God knows!; cf. also the elliptical Save us! Help us! Keep us! and the like; but the historical evidence is n…