So I am running across this construction in verbs while reading the prologue to the Canterbury Tales. It is to start certain verb forms with a y-

Some examples are:
Hath in the Ram his halfe cours y-ronne
Of sondry folk, by aventure y-falle (fallen)
For he was late y-come from his viage
At meet well y-taught was she with-alle
He hadde of gold y-wrought a curious pin
Is signe that a man is wel y-shrive
That unto logick hadde longe y-go (gone)
Her knyves were y-chaped noght with bras (mounted)
It is ful fair to been y-clept ma dame (called)
Ful many a draughte of wyn had he y-drawe (stolen)
His barge y-cleped was the Maudelayne  
The cause y-knowe, and of his harm the rote
Ful streite y-teyd, and shoos ful moiste and newe (tied)
Y-wimpled wel and on her heed an hat (kerchiefed)
And swich he was y-preved ofte sythes (proved)

In parenthesis are the translations given in the footnotes.

So it’s pretty obvious from the translations that they are past participles of the verb. So I’m wondering why the past participles of middle english verbs are constructed this way?
It’s also obvious from several of the examples that the form we’re familiar with in modern english- taught, wrought, tied, was already in usage. I’m assuming the form was drawn from an older form of saxon or gaelic maybe.  

I’m due to go work at the fireworks stand, so I don’t have time to look into this more right now, but I’m interested in why this is.