9: Eilo de Castil -New Name (NP)

Submitter desires a gender-neutral name.
Spelling (Eilo) most important.

Eilo: feminine Spanish given name dated 1097-1101 found in "Medieval Spanish Names from the Monastery of Sahagun, The Names, Second Group" by Antonio Miguel Santos de Borja (Tony Borning)

http://s-gabriel.org/names/miguel/sahagun/sahagunNames2.html

de Castil: Locative surname found in "Spanish Names from the Late 15th Century" by Juliana de Luna (Julia Smith)

https://s-gabriel.org/names/juliana/isabella/locative.html