An improved version, as corrected by The Furrow Collective's Rachel Newton:

The Cabin Boy
sung by Alasdair Roberts on The Furrow Collective: Fathoms

It's of a lady gay
And a lady fair and bright
She's fallen in love with a little cabin boy
And slighted lord and knight.

“Will you tarry on shore wi me, my boy?
Will you tarry on shore wi me?
I dinnae want any lord or knight,
My mind is bound to thee.”

“Gin your love for me is great,
Mine is greater still.
But ye maun to my captain gae
And speir for his goodwill.”

So she's to the captain gane,
“Grant me my Will,” said she,
“Gie to me your little cabin boy
To tarry on shore wi me.”

“And you a lady gay
And you ask me for a boy?
Better it be some lord or knight
Your sweet body to enjoy.”

So she's to her true love gane,
“Oh Billy, coo,” said she,
“The nearest and dearest of lovers we maun part
And sae maun you and I.”

Now Billy is on the sea
And the waves toss to and fro,
Crying like a little sea bird
From East to West he goes.

But they hadn't sailed a league on the sea
A league but barely four
Till the gallant ship and her men were lost
And Billy was never seen more.

It was in yon gairden green,
On green and grassy ground,
Early when her faither he arose
This lady's body he found.

Six maids dressed all in black
And six dressed all in green,
Her faither and mother a-mourning gaed
For she died for her cabin boy sae young.