Oana

The name is an ancestral Thracian/Dacian name (so Indo-European). It does not come from Ana or Ioana, which are both standalone names with the same origins.

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The fact that it is celebrated in the Orthodox religious calendar along with Saint Ioana is wrong. By those standards, half the Romanian girls' names should be celebrated then, too, considering most Romanians think these names are derived from Ana or Maria, and that they are Hebrew names, which they are not. They are Latin.

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The names Maria and Ana developed simultaneously with Miriam and Hannah, and this is due to an understandably limited and similar vocabulary at the time, for all languages. Similarly, Oana has no connection to the Hebrew-derived name Johanna.

It really doesn't come from Ioana. Both "Oana" and "Ioana" are derived from "Ana", and basically have similar meaning. They all mean something in the vicinity of "God was merciful". And the best way to pronounce it is like "wanna".