The wikipedia page on the Icelandic alphabet [0] sheds some light, þorn is runic, eð is from 'd'. Icelandic employs a 19th century reconstruction of the old no

The wikipedia page on the Icelandic alphabet [0] sheds some light, þorn is runic, eð is from 'd'. Icelandic employs a 19th century reconstruction of the old norse alphabet noting that "Various old features, like ð, had actually not seen much use in the later centuries" - which corresponds to their merger into one digraph 'th' in English. The article also notes that the letter ð undergoes a devoicing depending on its surroundings. [0] https://en.m.wikipedia.org/wiki/Icelandic_orthography#History https://en.m.wikipedia.org/wiki/Icelandic_orthography#Histor...