I think
Desmond is a good name suitable for any age.
Girly? I don't understand how this can be girly.
Will it be popular? I don't think it will come to the top of the charts very soon, and I agree with Array's reply on this.
I don't think of Lost!
Dezi is a cool nickname, as is Des. How about Mond is you're so afraid of it becoming feminine?