I am posting on behalf of my sister, who is expecting her second son in [name]September[/name].
She and her husband have tentatively decided on the name [name]Sullivan[/name] (perhaps [name]Sullivan[/name] [name]Edward[/name]) but really like the nickname [name]Saul[/name]. Is this usable?
We reason that [name]Saul[/name] for [name]Sullivan[/name] is every bit as sense-ical as than the commonly-used [name]Jerry[/name] for [name]Gerald[/name], but there does seem to be an issue with pronunciation: [name]Saul[/name] (sounding like “all”) versus Sull (sounding like “null”). What do you think?
Is the spelling Saulivan ridiculous? Any other cute suggestions for how she could get to nn [name]Saul[/name]?
Her first son does have a fairly traditional name, [name]John[/name] [name]Kelley[/name]. They most commonly use the double name, though he’s also referred to as J.K. and [name]John[/name]. [name]Sullivan[/name] is, then, in line with [name]Kelley[/name]'s Irish tradition.
Thanks!
I think that it’s absolutely fine to use the nn [name]Saul[/name] with the name [name]Sullivan[/name]. Many people who I know with nn have nothing to do with their name and it’s close enough. They should still spell it [name]Sullivan[/name] as Saulivan does look strange and is a creative spelling, which is something I can’t stand.
I agree with jtucker, although she would need to be prepared for most to assume a nn of Sull or [name]Sully[/name] which is usual for the name [name]Sullivan[/name] (from my experience anyway) 
Honestly, I think it’s ridiculous. [name]Saul[/name] and [name]Sullivan[/name] are completely different names. Saulivan is just silly.
My thoughts as well.
[name]Gerald[/name] to [name]Jerry[/name] is not the same thing since the nickname [name]Jerry[/name] has the same first syllable sound as [name]Gerald[/name].
[name]Sullivan[/name] is nice. [name]Saul[/name] is technically a completely different name. Maybe spelling it Soll would make more sense? If they don’t like [name]Sully[/name] as a nickname (it’s the most obvious), what about [name]Van[/name]? [name]Van[/name] would be a completely legitimate and easily spelled nn for [name]Sullivan[/name]. [name]Van[/name] works on a little kid and an adult. Have the considered it?
It doesn’t make sense at all to me. Why not [name]Ivan[/name]? Or Sed? Normally it’s [name]Ced[/name], short for [name]Cedric[/name] but Sullivan [name]ED[/name]ward could be Sed
ETA: If they want [name]Saul[/name] only as a nn, then they should go with [name]Solomon[/name]