The maid's well-known fear of the "mysterious" "foggy dew" may not be so very mysterious.

From John Bullokar's "English Expositor Teaching the Interpretation of the Hardest Words Vsed in Our Language"(16:

"Rime. A mist or foggie dew."

Rev. W. M. Trinder's "Twenty Practical Sermons" (1793): "Affliction thickens around us, like a foggy dew."

One assumes, then, that she was just trying to get warm. (Why she couldn't warm herself in her own bed is a different story....)

Steve, I first see the "foggy dew" on the Jennings broadside, "The Batchelor Brave," dated by the Bodleian to "1790-1840." Are you aware of a positively 18th C. "foggy dew" text?