The name Johanna came originally from Hebrew, and means "grace of the Lord". It is also reasonably common in many parts of the world. The names Jane, Joan, and Jessica derive from it and have the same meaning (in essence).
It's quite possibly one of the most confusing names in existence. It has at least four different basic pronunciations, most of which (to an English speaker, anyway) don't sound much like how it's written, and many variants thereof. It doesn't help that due to the law of conservation of correctness, you're almost guaranteed to pick the wrong one the first time. And the second.
jo-hannah - this is the easy one, pronounced essentially like it's spelled. Unfortunately, in my experience also the least common.
joanna - likely the most common version, it has that tricky silent h. Not to mention that 'Joanna' is also a name, so even hearing it can be confusing.
yo-anna - an odd mix, this one. And it has another tricky letter, a Dutch/German j, plus the silent h.
yohanna - a little less tricky than the previous version, but still less than obvious. I'm also told that at least in its Dutch incarnation, it should be pronounced closer to a flat yohunna. Quite common in The Netherlands and parts of Europe, less so elsewhere.
With this, you at least stand a fighting chance of making the correct choice of pronunciation or spelling. Of course, it's inevitably the wrong one. It never occured to me that "Johanna" I read was the same as "Yohunna" I spoke to until I saw her name written. Perhaps I'm just ignorant, but I wish I'd known this.