What is the meaning of prefix -y in the following examples? [duplicate]

Question

These are some exmaples from Choser:

1)He was war of me, how у stood
Before hym and did of myn hood,
And had ygret hym as I best koude.

2)A certein tresor that she thider ladde,
And, sooth to seyn, vitaille greet plentee
They han hire yeven, and clothes eek she hadde...

3)For he was late уcome from his viage,
And wente for to doon his pilgrymage

I guess the meaning of -y can vary, because in 1) it seems like it`s just playing a part of "I":

And had I greeted him as I best could

And in 2) it looks like a phonetical construction:

"y"+e = "gi:"
yeven=given (?)

But I'm not sure at all about those as well as I'm not sure about the third example (maybe it's pronoun again), the meaning of which I can`t even guess now.

Answer 1

A past participle form from Old English ge-:

Y- :

The prefix ge-, a regular past participle marker in Old English, continued to be attached to the past participle throughout the Middle English period. Over time, however, the attachment of ge-, which weakened to a form spelt y- (or i-), be- came no longer obligatory. The Northern dialects eliminated the prefix, leaving suffixes as the sole markers of the past participle. In the South, y- was still used, but optionally, especially in Late Middle English, with a steady increase in the use of forms lacking prefixal marking.

(www.peterlang.com)