I think Jon’s on the mark describing this as “A bit of a classic. I’m not sure where it comes from – it’s fairly ubiquitous, although I s’pose I associate it most with Lou Killen. It’s unusual in that it’s a folk song actually celebrating chastity…”
Cryril Tawney is credited for unearthing this and Tony Rose and then Lou Killern for taking it on, at least according to this Mudcat thread. It only seems to have been collected twice, but about half way down that thread you’ll find a link though to ‘Twas On A Monday Morning O that refers to a song called Green Willow (that song is then transcribed in another post just below), which shares much of this. I’m rather taken with June tabor’s notes on Mainly Norfolk that seem to indicate how widely kown this song had become on the circuit. It’s not entirely surprising, as it is lovely and Jon’s guitar adds a certain something that instantly makes this a great start to the month.