[name_f]Olivia[/name_f]
[name_f][/name_f][name_f]Oona[/name_f]
[name_f][/name_f][name_f]Odette[/name_f]
[name_f][/name_f][name_f]Olivet[/name_f]
[name_f][/name_f]Odelia/Odilia
[name_f][/name_f][name_f]Olivie[/name_f]
[name_m]Owen[/name_m] (though I prefer Eoghan)
[name_f][/name_f][name_m]Octavian[/name_m]
[name_f][/name_f][name_m]Oskar[/name_m]
[name_f][/name_f][name_m]Orion[/name_m]
[name_f][/name_f][name_m]Odin[/name_m]
[name_f][/name_f][name_m]Olaf[/name_m] (though I’m not sure it’s usable after Frozen)