A couple of my old ancestors born in the early 20th century got the name Jarlath. They were 3rd-generation Irish in Illinois. One went by Jay. One of them spelled it "Jarleth" and I kind of like that spelling better, although it's incorrect. I like the name but honestly I would not burden an American boy with it in this day. But Irish names are still popular so maybe Jarlath will spring up in some circles.