Explanation of a sentence in "Adam lay ybounden"

Adam lay i-bowndyn

The text you are citing, commonly known as Adam lay ybounden, is a text from the 1400s preserved in a single specimen. The original text was not spelled as you have it. Rather, it was written like this:

Adam lay i-bowndyn,
          bowndyn in a bond,
Fowre thowsand wynter
          thowt he not to long

And al was for an appil,
          an appil that he tok.
As clerkes fyndyn wretyn
          in here book.

It doesn’t really have a “title” per se; rather, as is oft done, it is known by its first line.

Fynden

Yes, fynden is not a past participle. It might be a present plural which would be the same as the infinitive, and it might just possibly be a past tense plural. In any event, it matches number with clerks. In Modern English, that would be

“And all was for an apple,
          an apple that he took
as clerks find (or found)
          written in their book.”

^{(Sorry, but modernizing it kills the scansion.)}

There were regular base forms of the verb like _^FYNDEN and _^FINDIN, which would be the same in the infinitive as in present plural just as today. So perhaps this is just another spelling of one of those two.

The quality of the vowels suggest it was not a past tense, although there was a _^FYNDON in the 12ᵗʰ century; as a macaronic text, it might grab that, although I’m not convinced. The OED lists the past tense plural forms of find as:

1 _^FUNDON,
(2 _^FYNDON),
2–4 _^‑EN,
3–7 _^FOUNDEN,
(4 _^FOUND‑, _^FUNDYN,
6 Sc. _^FUNDIN),
4–5 _^FONDEN,
3–5 _^FOUNDE,
5– _^FOUND,
Sc. 4– _^FAND,
(9 dial. _^FANT).

As you can see, there were a lot of ways to go out at it, and given the macaronic nature of this text, I would not put too much in finding one form one place and another form another place. It’s made up of many stray bits.

I-bowndyn

Past participles beginning with y- are archaisms left over from Middle English and Old English. They are cognate with modern German participles like gebunden. You can find the word written in a more German way in Beowulf:

Cyninges þeʒn··word oþer fand soðe ʒebunden.

The OED’s last two citations for ybound are:

• 1647 H. More Song of Soul ɪɪ. Democr. Plat. ᴠɪɪɪ, ― The low Cusp’s a figure circular, Whose compasse is ybound, but centre’s every where.
• 1714 Gay Sheph. Week Prol. 84 ― Thy joyous Madrigals twice three, With Preface meet, and Notes profound, Imprinted fair, and well y‐bound.

Why was it not ʒewriten as in Old English or ywriten or ywryten as in Middle English? In part because the y- forms died out at different times in different places, but also because here the scansion seems to call for it. It might also be an intensifying version of the past participle.

There was some restoration of y- forms like yclad and yclept as deliberate archaisms by some. The OED writes:

The general facts of the history and survival of OE. ʒe-, of which some details are given below, are :– In positions where it was still recognizable as a prefix, it had left few traces in northern English by 1200; its disappearance in the north was assisted by the absence of the prefix in ON. Substantival, adjectival, and verbal forms (other than pa. pples.) continued, not later than the end of the 14th century, only in southern and west-midland dialects. The pa. pple. was regularly formed with the prefix in southern ME. till about the middle of the 15th century, and its use in the form a- survives in south-western dialects to the present day. Pa. pples. so formed were a prominent feature of the archaistic language of Spenser and his imitators, and a few of them, the most notable of which is yclept, persist as conventional archaisms of poetry.

So now and then you will see these used even today by archaizing writers, mostly poets.

What many people don’t know is that we still use its remains today without noticing them or thinking about it. For example, handiwork decomposes to hand + i-work, and was written handʒeweorc in Old English. There are several other examples like that, such as how close enough really used to be to modern German genug back when it was written ʒenoh, or how aware was once ʒewær.

There need be no y- before fyndyn, because it's not completed, i.e. the clercs still can read the story in the (holy) book.

From Online Etymology, y- before a verb put it in the past tense (with an element of with):

y-: perfective prefix... a completive or perfective element... Among hundreds of Middle English words it formed are yfallen, yhacked ("completely hacked," probably now again useful), yknow, ymarried, ywrought.

"Adam lay ybounden" means Adam lay bound/Adam lay completely bound (by his sin).

There need be no y- before fyndyn, because it's not past tense, i.e. as clercs find this (hire) book.

Again per Online Etymology, the word "find" was findan:

Old English findan "come upon, meet with; discover; obtain by search or study" (class III strong verb; past tense fand, past participle funden), from Proto-Germanic *finthan "to come upon, discover" (cognates: Old Saxon findan, Old Frisian finda, Old Norse finna, Middle Dutch vinden, Old High German findan, German finden, Gothic finþan), originally "to come upon." To find out "to discover by scrutiny" is from 1550s (Middle English had a verb, outfinden, c.1300).

We find the y- again before Oure Lady 'having been made Queen of heaven'. (Interestingly, we find it again in front of syngyn?)

The text of the carol (Sloane Manuscript 2593 in the British Library):

Adam lay ybounden, bounden in a bond,
Four thousand winter thoughte he not to long;
And al was for an appil, and appil that he tok,
As clerkes fyndyn wrytyn, (wrytyn) in hire book.
Ne hadde this apple taken been, this apple taken been,
Ne hadde nevere Oure Lady (ybeen)* (hevene) Queen.
Blessed be this time that apple taken was:
Therfore we mown y (?) singen Deo Gratias.

The original text:

I think it simply means (basically and somewhat paraphrased, but I think correctly)

Adam lay completely bound, bound in a bond,
Four thousand winters thought he not too long;
And all was for an apple, an apple that he took,
As clergy find written, written in this (here) book...

I think additionally that it is interesting that a similar sign meant th as you can see in the original text, in "that he tok, this appil,

• not in the original but in transcriptions