[colechristensen]

"Ye Olde Mill" or whatever archaic silliness you'll find at fairs and whatnot was the result of the printing press dropping þ (as in þe, þ is just th-) and was never supposed to be pronounced with a "y" sound.

"Ye Olde" ye was not the same word as "Hear ye, hear ye!", that ye is a plural 'you' basically the same word as "y'all" and never had a thorn.

[tengwar2]

This happened with more than one letter. For instance the Scots language had a letter yogh (https://en.wikipedia.org/wiki/Yogh), which was written somewhat like a rounded "3" but lower on the line. Early printers had only the characters of the English language, and since this character looked like a hand-written z, that is what they used in its place. Hence the name "Menzies" is pronounced "Ming-is", since that isn't actually a z.

Welsh suffered more: it used to be full of "k"s. When the first Welsh Bible was printed, the English printer did not have enough "k"s, and substituted "c", and the language now does not use "k" at all. Apparently the printer's note on the matter still exists.

[cguess]

Just to expand on this:

"ye" in "ye Olde mill" is actually just "the" but originally "þe"/"þee". The first printing presses to England were imported from Germany, which never used þ, so printers used something that looked sorta similar, thus "y".

"Ye" was a different word, the 2nd person non-formal version of "you" (which was historically formal: see-Shakespeare and how he played with "ye" and "you"). Thorn was on its way out along with "ð" both of which were in Middle English. The sounds didn't leave English, but we merged it into one letter cluster "th" (think "that" and "the", which have different th sounds).