Dany was most like named by her mother, Tyrion by his father, Jon by Ned.
Since all of their mothers died, who gave Jon Snow, Daenerys Targaryen, and Tyrion Lannister their names?
Notice how Martin mentioned Tyrion being named by his father (for simplicity’s sake, let’s hold off on any non-Tywin theories), but immediately thereafter made separate distinctions for Jon and Ned?
Mothers can name a child before birth, or during, or after, even while they are dying.