*(or 7 or whatever number makes you feel best)
In Unicode, that's ſ and þ. Both historical English letters that are no longer used.
"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.
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.
"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).
And while not encoded on a keyboard, it still blows my mind that English has a crazy number of past tenses - and a such a bad hack of a future tense that it’s hard to classify as such.
Linguistics is fun. The accents are alright.
This was caused by the printing press and the typewriter (keyboard) both of which forced simplifications in the written English language.