Well, hip isn't necessarily equal to popular. I think that a lot of the names that were specifically popular around the turn of the 20th c. - 1920s have a particular image that is fashionable right now.
Viola and
Frances included... they give me the same impression as a lot of the not-so-common but still very fashionable sounding names I see on babies lately.
Such as ...
Popular -
Ella,
Stella,
Bella,
Grace,
MadelineUncommon but still fashionable in the same way, to my mind at least -
Eleanor,
Lillian,
Hazel,
Violet,
Evelyn,
Lucy
Olive is another one that I've seen on a child recently that I'd put in this category .. of "hip antique" name fashion. If I met a baby
Viola I'd also put it in the "hip antique" box. I don't mean I think it'd be bad in some way to use these names, though. There's something to recommend having a name with the "right" fashion date on it, and it's hard to avoid the idea of fashion altogether (although it's hip to try).