Wow, two questions in one day I feel qualified to throw an answer at.

So, the letter that is often transcribed from early modern texts (the KJV and other Bible printings of the period in particular) as a "Y" or "y" is most often actually a printer's way of saving money on type blocks by substituting those letters for the letter commonly called a Thorn - written as Þ or þ originally, but later becoming more like another old character, the wynn - Ƿ, ƿ - when written.

Early modern authors often used several abbreviations when writing common words - including the and that. These were written using stacked letters, so you ended up with a ƿ with an e or t on top of it, joined across the arc of the shape at the top. Thus, if you remove the t or e, you got what commonly looks like a very fancy "y".

You can read more about this here or here.

Now, this is NOT to be confused with the word "ye", or sometimes "yee", the second-person, plural, personal pronoun (nominative form). This was carried over into middle english from old english, which used "ge" as this pronoun. In Middle English one used "ye" when addressing more than one person as a "you", while one would use "thou" for addressing a single person as a "you". In fact, second person pronouns in all three forms had distinctions between singular and plural forms in Middle English. Thus, if speaking to one person, I would say "Thou" are coming with me, but if to more than one, "Yee" are coming with me, all together!

The "yee" plural form survives in some dialects of Scots-English and Appalachian English, as a distinct word. It is the equivalent, in fact, of the y'all we use down here in the Southern US!

You can read more about this here.

You can try asking r/asklinguistics as well