I like nonsense names that are easy to spell and pronounce but I am struggling to find a truly timeless name.
I take it you meant to type 'no nonsense'. There are loads of truly classic names, but that's not to say they won't occasionally pick up massively in popularity for a decade or so, then dip back into relative obscurity but still be considered a classic. When I was a child no-one except people's grandads were called George or William or Harry or Charlie. Very, very few people my own age were called that, whereas James is the epitome of a true classic that never goes out of use or style. Now there are tons of young people called William, George and Henry and Charles. They are all classic names but ones that fell out of popularity in the 50's 60s, 70's and 80s, then had a resurgence in the 90s and ever since.
For girls I think true classics that are pretty hard to date irrespective of the occasional popularity spike are:
Anna, Emma, Elsa, Erin, Erica, Ellen, Eleanor, Lara, Tara, Vanessa, Rachel, Hannah, Sarah, Sara, Kate, Esther, Eve, Elizabeth, Imogen, Martha, Catherine, Victoria, Isobel, Abigail, Rebecca, Phillipa, Zoe, Nicole, Jennifer, Rose, Verity, Annabel, Penelope, Phoebe, Charlotte, Diana.