The rather shorter version that Bert used to sing surely originated [or at least was collected from] Harry Cox; or perhaps one of his Norfolk predecessors, from whom older collections contain several of what are often thought of as 'his' versions.

I seem to recall a lot about the symbolism of 'dew' to represent virginity in the intro to James Reeves's The Idiom Of The People; shall go back there and check.

~Michael~