It may not help much, but Ostiane seems to have a male counterpart in the name Ostian.
There was a 6th century saint in France of that name. Some info about him, in French:
http://nominis.cef.fr/contenus/saint/10149/Saint-Ostian.html
Here is some frequency information about Ostiane in France: Only 17 since 1946, indeed quite rare:
http://www.aufeminin.com/w/prenom/p15299/ostiane.html
Rene
www.BabyNames.ch