In outline, Irish mythology (sources like the Lebor Gabála Érenn) says Ireland was occupied by the Túatha Dé Danann (a magical, beautiful, ethereal race), before the Milesians (Celts/men) took it. ‘Túatha’ is a word without English equivalent, meaning clan or tribe or petty kingdom; ‘Dé’ means ‘gods’; and Danann is the genitive form of Danu so it means ‘of Danu’.
Meanwhile, over in India, we read in the Mahābhārata that the goddess Danu gave birht to a race of asuras (demigods) called the Danava.
There’s lots of these little Indo-European links – in language, in culture, in myth. You see more and more of them the longer you look.
Some of the shared mythology about rescuing someone from the underworld but being unable to look at them during the rescue is interesting. Orpheus and Eurydice, Lot and his wife, Izanagi and Izanami. Makes me wonder why that seemingly popped up in multiple cultures.
Also thought to be linked to the names of many great rivers. Danube, Dan, Don, etc.