The post name is
ILANA, not a Welsh name. The Welsh name which she proposes is
Claerwen. It is a place name (a river in Powys) used as first name in Wales (an example is Claerwen
James); it comes from the Brythonic roots
claer, "bright", and
gwen, "white, fair, holy". Since the place name ends in
(g)wen, the name is used as feminine name.
Here you have a link to the only reliable online source in Welsh names that I know:
A-M
http://kimkat.org/amryw/1_enwau/enwau_bedydd_cymraeg_geiriadur_1_1265e.htm
N-Y
http://kimkat.org/amryw/1_enwau/enwau_bedydd_cymraeg_geiriadur_2_2524e.htm
Lumia
http://onomastica.mailcatala.com