I love the name [name_m]Oslo[/name_m] but know it would be connected to the city in Norway every time and I don’t love the idea of destination names, especially uncommon ones. However, I love the sound of [name_m]Oslo[/name_m]. Is there any names you can think of that [name_m]Oslo[/name_m] could be a NN for?? I think it would be a super cute NN and wouldn’t have an issue with it being a NN for a long form name 
Since you don’t like the idea of an obscure location full name what about [name_m]Orlando[/name_m] (this is more common) or [name_u]Arlo[/name_u] instead of [name_m]Oslo[/name_m]?
Or [name_m]Osborn[/name_m] nn [name_m]Ozzy[/name_m]?
Full name ideas for [name_m]Oslo[/name_m] (Favorites in Bold):
[name_m]Orlando[/name_m], [name_m]Oswin[/name_m], [name_m]Oliver[/name_m], [name_m]Oscar[/name_m], [name_m]Otis[/name_m], [name_m]Oswald[/name_m], Oleander, [name_m]Olaf[/name_m], [name_m]Olsen[/name_m], [name_m]Osborn[/name_m], Orwell
You could also pair the first and middle name to complete the nn [name_m]Oslo[/name_m]… example, [name_m]Oscar[/name_m] [name_u]Lionel[/name_u], [name_m]Ozzy[/name_m] [name_m]Lance[/name_m].
[name_m]Lorenzo[/name_m] could work as well.
Onslow, Oswald, Oswell, Oslyn, Olsen, Ozell, Oziel, Laszlo, Winslow, Sloane, Bosley, Mosley, Alonso…
Oscar Lorenzo? Ozias Logan? Oswin Lorne?