This text was first published in Folk Songs from Somerset, vol.I (1904; ed. Cecil Sharp & Rev. Charles L. Marson), with the remark, "Mr. Marson has re-written the words, retaining as many lines of Mrs. Hooper's song as were desirable.".  The book was intended for a "genteel" readership, so references which risked offending the sensibilities of the time were often removed.  James Reeves (Idiom of the People, 1958) says:

"In fact no more than six of the twenty-seven lines are more or less as dictated by the two sisters at Hambridge, in the winter of 1903.  This harmless composition, reminiscent of William Morris in his more sentimental vein rather than of any folk song original, completely suppresses the real situation and eliminates the essential spirit of the song.  Sharp appears to have thought that in this case Marson went a bit too far, for he did not reprint The Foggy Dew in any of his later publications."

This is the song as Lucy White and Louie Hooper actually sang it (from Sharp's ms., reprinted by Reeves):

One night as I lay on my bed,
As I lay fast asleep,
A pretty maid came to my bedside;
Most bitterly she did weep.

She wrung her hands and tore her hair,
Crying, asking what shall I do?
Come into my bed my fair pretty maid.
For fear of the foggy dew, dew, dew,
For fear of the foggy dew.
So there they laid all that long night.
Till daylight did appear;
Come rise, pretty maid and don't be afraid,
For the foggy dew is gone, gone, gone
For the foggy dew is gone.

I never told her all her faults
And I never do intend so to do,
But there's many a time I've rolled her in my arms,
For fear of the foggy dew, dew, dew,
For fear of the foggy dew.

Sharp collected a number of versions, many more complete than this one.  The song was widely popular in England, and was regularly printed on broadsides in a number of forms.  It dates back at least as far as 1689, when a broadside entitled The Fright'ned York-shire Damosel, or, Fears Dispers'd by Pleasure was published by J. Millet.  Robert S. Thomson goes into the song's genealogy in some detail in his article, The Frightful Foggy Dew (Folk Music Journal vol.4 no.1, 1980)

There's an article by Bruce Olson in the same issue, incidentally.

Malcolm