These are their stories.
…I miss Law & Order.
Yogh (capital Ȝ, small ȝ, although it evolved over time much like other letters) came from an Old Irish form of the letter g. The pronunciation was a hard, throaty y-g sound, if that makes sense. Because it looked like a Z, a lot of words that were supposed to have yogh instead had a z. It’s how the name Mackenzie got its Z.
Thorn (capital Þ, small þ) is one of the old th sounds. It has a straightforward pronunciation, like th in math or thesaurus. The reason old timey signs say “ye” is because that y is supposed to be a thorn, making it “the”. It’s because thorn kind of looked like a y in some of its evolutions.
Eth or edh (capital Ð, small ð) is the other of the old th sounds. It’s pronunciation is much softer than thorn’s, more like if you barely said the th (compare how hard you th when you say the word “math” to when you say the word “this”).
Wynn or wen (capital Ƿ, small ƿ), from an old runic alphabet, is an old character for w back before w existed. When W showed up, wynn wasn’t cool anymore and faded into obscurity.
And there are plenty more where those came from, but I’ve bored you enough for today.