humans just put certain expectations into the word.
… which is entirely the way words work to convey ideas. If a word is being used to mean something other than the audience understands it to mean, communication has failed.
By the common definition, it’s not “intelligence”. If some specialized definition is being used, then that needs to be established and generally agreed upon.
It’s eth, actually, not thorn.
I had thought that eth was used in Old English for the voiced “th” and thorn for the unvoiced “th”, but Wikipedia says they were used interchangeably for both sounds.
You’re right otherwise. Thorn was not available on printing presses because they were being made in countries that didn’t use the letter, which is why the letter Y was used instead until “th” became more common.
https://en.m.wikipedia.org/wiki/Thorn_(letter)
https://en.m.wikipedia.org/wiki/Eth