"Hippie yippee hobo free spirited rainbow-ish" comes closest.
I would just say it's flaky or eccentric, which isn't totally negative to me, it just isn't quite my taste. I like some names in the category. But Prairie is hard to say because of the R's, like
Aurora, and it seems sort of, hm, precious? ... prayer-y, and Little House on the.
- mirfak