I always kind of conjured up rather comical images upon hearing the line
"We'll tie blue ribbons all around his head to let the ladies know he's married."

But recently I found one of the other variations on the lyrics and saw the line as
"We'll tie blue ribbons all around his hat ... "

That makes a lot more sense to me and conjures up a far less silly image.   
Dare I assume that the "head" version was originally a mondegreen?
Or was there really a British Isles tradition of tying a lot of blue (or green) ribbons around a guy's head as a sign he had a wife?


I also like the verse about the young woman and her barely pubescent husband finally getting some 'alone time' (the specifics vary from version to version) and her "never more complain(ing) of his growing."   Not sure who all includes that verse, but one version of it is:

Now down into the college park
They walked about till it was dark,
Then he lifted up her fine Holland sark,
And she had no reason to complain
Of his growing, growing, &c.

Not the first version of this verse I heard, but basically the same concept.