'Tis a fairly easy song with a simple chord progression so I'll omit it for most of the verses.
Listen to the song and you'll get the rythm (obviously)

Capo on 3rd Fret

Intro
C , F , C , G  C , F , C , G , C  C , F , C , G  C , F , C , G , F

Verse
C                F                 C              G
Once there was a shepherd lad kept sheep upon the hill
        C                     F               C          G         C
An he's laid his pipe and his crook aside and there he's slept his fill. 
C               F              C        G
He woke up on a riverbank on a fine May mornin,
    C                F                    C            G       C        F
And there he spied a lady swimming in the clothes that she was born in.

         
So he raised his head from his green bed and he approached the maid.
"Put on yer claithes, my dear," he says, "and do not be afraid.
It's fitter for a lady fair to sew a silken seam
Than to rise on a fine May morning and swim against the stream."


"Well, if you'll not touch my mantle and you'll leave my claithes alane,
Then I'll give you all the money, sir, that you can carry hame."
"I'll not touch your mantle and I'll leave yer claithes alane,
But I'll tak you out of the clear water, my dear, to be my ane."


An' he's taen her oot o the clear water and he's rowed her in his arms.
"Put on yer claithes, my dear," he says, "and hide your bounteous charms."
   F            C                     F     C     G
He's put her on a milk white steed himself upon another,
         C             F                  C      G        F       
And it's all along the way they rode like sister and like brother.


Instrumental
C , F , C , G  C , F , C , G , C  C , F , C , G  C , F , C , G , F


She rode intae her faither's gate and she's tirled at the pin,
And ready stood a porter there to let the fair maid in.
When the gates were opened, it's so nimbly she stepped in.
She said, "Kind sir, you are a fool without and I'm a maid within.


"So fare thee weel, my modest boy. I thank you for your care,
But had you done as you desired, I'd never have left you there.
F             C                F    C   G          
I will sew no silken seam on a fine May morning.
        C                        F                 C         G
You can bide your time till your time runs out, so take this as fair 
C
warning." 

F             C                F    C   G          
I will sew no silken seam on a fine May morning.
        C                        F                 C         G
You can bide your time till your time runs out, so take this as fair 
C
warning." 


Outro
C , F , C , G  C , F , C , G , C  C , F , C , G  C , F , C , G , C


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