—— folk family and jam

Knight of the North country

An outlandish knight from the North land came
And he came a-wooing of me
And he told me he'd take me to that Northern land
And there he would marry me

Well go and get some of your father's gold
And some of your mother's fee
And two of the very best stable steeds
where there stand thirty and three

So she borrowed of her father
And some of her mother's fee
And away they did ride to the fair riverside
Three hours before it was day

Alight alight my pretty Polly
Alight alight cried he
For six pretty maidens I've drowned here before
And the seventh thou'rt to be

Pull off pull off your silken gown
Deliver it unto me
For I think it too fair and much too fine
To rot in the saltwater sea

Well go get a sickle to crop the thistle
That grows beside the brim
That it may not mingle with my curly locks
Nor harm my lily white skin

So he went and got a sickle to crop the thistle
That grew beside the brim
And she cast around him around the middle so small
And tossed him into the stream

Lie there lie there you false hearted man
Lie there instead of me
For six pretty maids thou hast drowned here
And the seventh has drowned thee

She mounted upon her lily white horse
And she did ride away
And she did reach her father's own gate
Three hours before it was day

Now the parrot being up in the window  so high
Hearin the lady did say
I fear some bold ruffian has led you astray
That you've tarried so long away

Don't prittle or prattle my pretty Polly
Nor tell no tales of me
And your cage it shall be of the glittering gold
And your perch of the best ivory

Now the master being in the bedroom so high
Hearing the parrot he did say
Now why do you prattle my pretty Polly
so long before the day

Oh there came an old tom-cat up on my cage
To take my sweet life away
And I was just calling my mistress dear
To scare that old cat away

From Tom obviously.

Another of these abduction / seduction songs.  Interesting here in that the motive is explicit; a serial killer; and of course turning the tables.  There are several versions with a parrot who may or may not be silenced by promises of golden cages; several versions without the parrot. 
There are various versions of the trick used.  More feasible (if that has any meaning here) - and more interesting - is the one where she asks him to turn his head as she undresses.  Where would he have got a sickle from?
Child Ballad 4.  From the 18th century.  Another version is called Lady Isabel and the Elf Knight, though there is no mention of the name Isabel, nor any indication that the knight is an elf.