I love [name_f]Louisa[/name_f], [name_f]Luisa[/name_f], [name_f]Lucy[/name_f], [name_f]Luna[/name_f], [name_f]Lucia[/name_f]…The list goes on. Lately my favorite has been the simplest, [name_u]Lou[/name_u]. [name_f]My[/name_f] only concern is that it’s far too close to loo, as in the informal British term for the bathroom 
I’m in the States, but everyone knows what “the loo” means, even if it’s not in common use. [name_f]Do[/name_f] you think this would be an issue? If yes, which of the above [name_u]Lou[/name_u]-[name_f]Lu[/name_f] names is your favorite?
I don’t think it’s much an issue, at least from my perspective here in the States. [name_m]Even[/name_m] so, if it sticks in the back of your head too much, it probably is an issue. Out of those I like [name_f]Lucia[/name_f].
I don’t think many in the U.S. [name_m]Will[/name_m] make that connection. But, I love [name_f]Lucille[/name_f] and could go with the nn [name_u]Lou[/name_u]. [name_f]Louisa[/name_f] is nice because it would have a similar spelling then. [name_f]My[/name_f] aunt is [name_f]Bonnie[/name_f] [name_u]Lou[/name_u], so it may not be as rare as you think.
Loo has never entered my mind when saying [name_u]Lou[/name_u] for some reason, I know a [name_f]Louisa[/name_f] and my middle name is [name_f]Louise[/name_f]. I like [name_f]Luna[/name_f] and [name_f]Lucy[/name_f], I’ve also heard of a [name_f]Luciana[/name_f].
I don’t think it would be an issue here (in Australia) - I mean [name_u]Lou[/name_u] is established well enough as a name that it has a very weak (if apparent at all) association to the slang.
I personally would prefer a [name_f]Lu[/name_f]- name with [name_u]Lou[/name_u] as a nickname though, regardless of your concern, in which case [name_f]Luna[/name_f], [name_f]Lucia[/name_f] and [name_f]Luisa[/name_f] are my favourites.
I don’t think it would be an issue: [name_u]Lou[/name_u] has long been an accepted name, and there are many other long accepted names that have odd / negative meanings as a word, but because they have been a name so long, nobody really sees that anymore (e.g: [name_m]Rob[/name_m]).