Is that straight from the RAW or a translation? Because the katakana is saying Yuuhabaha.. Which is very different from Yhwach? Any Germans can verify that Yuuhabaha sounds anything like Yhwach? Or vice-versa.
In my view, Bach's name is quite confusing to comprehend because Kubo used Japanese letters for the pronunciation of what appears to be a German-esque name, which is also being written with English letters. The above picture posted by clydu is from the raw version of volume 58, but as anyone can see, the names are written in both English and katakana.
The English would likely carry the pronunciation, "You-Walk," without trying to apply a German accent/pronunciation. However, with a German context added, the pronunciation (according to a close friend of mine who's fluent in German) would be akin to "Yee-Ha-Vok" (that is, after changing the English letters into a more-appropriate, German-sounding name). The katakana definitely reads as "Yuhabaha," and that is where the problem lies.
Kubo has essentially given Bach two different names using three different languages (if that makes any sense). One name, included in chapter 505, is "Yuhabaha" due to the katakana characters, but after being romanized, you end up with either "Youwalk" or "Yeehavok." BadKarma was also very confounded by the name, and posted a comment telling the readers to wait for Kubo's "official" spelling. For all we know, this could very easily turn into another one of many names in the manga universe which have distinct spellings when compared to their pronunciations.
It's like Harribel's first name: the katakana is "Tia," yet the English is written as "Tier," which provides a different pronunciation.
Edited by PlasmaWolf, 10 March 2013 - 10:57 PM.