Hey,
Was wondering what the significance of the number 33 is in folk music? Often comes up as "by thirty and by three",
Such as in Willy O' Winsbury:
"and the king has gathered his merry men all,
By thirty and by three"

and in The False Hearted Knight:
"So she brought him out her fathers gold,
And her mother's jewels brought she,
The two best horses that stood in the stalls,
Where there stand thirty and three"

Any help would be appreciated to satiate my curiosity.
Also feel free to point out any other examples where this occurs.