It's a pretty sound, but it's akin to naming your daughter Praise The Lord or Rejoice. It's really, really tacky and borderline disrespectful as a name.
Seriously?
Hosanna has a history of use (as does Rejoice, for the record). Whether you find it disrespectful is one thing, but it seems a tad ridiculous to me to term it not a name. It's been used as such for quite a while--perhaps not commonly, but it's certainly not out of left field.
Array