Good Luck With This One..

[faggy]

The use of "YE" as an archaic form of "THE" derives from a misreading of an Old English letter whith what name in fact, pronounced "TH".........Any answers much appreciated !!!

[Ken4155]

Thou

[Cloverjo]

I remember this being discussed on QI a few years ago. I think it's called a thorn.

[elliemay1]

Just to confirm Cloverjo's answer:

//The use of the term ye to mean "the" derives from Early Modern English, in which the was written þe , employing the Old English letter thorn, ⟨þ⟩.//