I find this all very interesting even though its not answering my original question :-)

Whatever the origins of our customs, thanks Bill for distingushing them from rituals which to me smacks of outdated superstition ie if I dont slaughter a virgin the sun wont come back next year(!), I think its important to keep them alive as part of our heritage.Even if they are only a couple of hundred years old our fathers and grandfathers still observed them and thats enough for me. After all I wouldnt dream of not putting up a Christmas tree and thats only custom in England since Victorian times.

Originally I was just wondering why everything in folk songs happens in May...murders, shipwrecks, mining disasters, the lot! Possibly May just rhymes with more things than February...