Re: What are the criterion of timeless name?
Which name are you talking about?
I think when a name first becomes popular and then has a decrease in popularity, it's heavily associated with that one decade/generation/whenever it was the most popular. But if it gets popular again and has multiple phases of popularity, it becomes timeless because people don't associate it with one age. And what Dianatiger said, it depends on regional trends that you won't always know about just from looking at nationwide name data.