Where does “þriðjudagur” come from?
þriðjudagur (Icelandic) comes from Icelandic þriðji, from Old Norse þriði, from Proto-Germanic þridjô, from Proto-Indo-European tretyós, from Proto-Indo-European tr̥tyós, from Proto-Indo-European tréyes — three.
þriðjudagur (Icelandic): Tuesday
Ancestry of “þriðjudagur”, step by step