OK
Only in very special cases.
Like being named Pope.
There are two villages named Ratzing in Bavaria, both now part of larger municipialities, Ampfing and Waldkirchen, respectively. As you can see on the maps accompanying the articles, both are not far from Marktl, Ben XVI’s birthplace, so the most likely explanation is that one of his ancestors moved from one of those Ratzings and got dubbed Ratzinger i.e. the one from Ratzing.
I haven’t looked at the etymological origin of his name - if there is a certain one, which is not given - but I see a problem with your theory, since Rat (counsel) is pronounced with a long “a”, as would be combinations, but Ratzinger is spoken with a short “a” and the stress on the “tz”.
Also, I have never heard the term of “Ratsänger”; a towncrier would be Stadtschreier.
Well, it does allow the abbreviation to “Ratte” (rat), though - although I picked that up more from Rat here on the Dope. Common here is “Ratzi”, not as endearment, just shorter.
Well, benedict means not only “well said” or “speaking well” in Latin, it also means blessing “Benediction”. But since we don’t know what Ratzinger means, how can it be related to Benedict??
German Wikipedia, citing a book on the meaning of German names, agrees that the last name of Ratzinger comes from the town of Ratzing (or as patronymic to the first name Ra(t)zo, but in this case, that sounds unlikely).
Since both villages of Ratzing have now become part of bigger towns, as Mops notes, Wikipedia doesn’t explain where that name comes from.
The -ing suffix is from the time of the big Migration period, and is a genetive/ possesive form referring either to a place or a person (again) - so some guy named Rats or similar settled down and the village Ratzing was named after him.
Not Darth Vader, but Darth Sidius.
He’s also known on the web as Pope Palpatine.
The surname Ratzinger actually means “of the locality Ratzing” in Bavaria as previously mentioned. Furthermore, Ratzing means “the settlement of Ratzo” or “the settlement of a counselor”. There, now the people of Google will know. 
It means “Rizzo’s one-liner”.
Or joining a religious order, for example, taking vows as a nun. Or actually, confirmation, although in Australia, it’s unlikely that many people would actually go to the trouble of using a confirmation name in civil society.
The thing about being pope is that when he gets a (papel city) passport and drivers licence in any name he wants, his secratery can write to all the credit card companies and to the moter vehicle registration department.
Anyway, when you are young your parents choose your name and the clothes you wear. When you grow up, you can choose your own clothes and name.
Ratzinger means that someone has origins in the town of Ratzing. There are several German towns with this name. RATZ means ‘Serb’. Serbs were indigenous people in Germany, and many German cities originally had Serbian names (Berlin, Dresden, Leipzig, Brandenburg). So, the meaning of the surname Ratzinger is – someone who has origins from the city named after the Serbs.
Did you mean “Sorbs” when you wrote “Serbs”?
And while “Benedict” does mean “speaking well”, or something related to that, he almost certainly chose the name, either directly or indirectly, in reference to Saint Benedict, the founder of one of the larger religious orders in the Church (“indirectly” meaning that he might have been choosing to honor someone else who was named after the saint, such as any of the previous 15 popes who bore that name).
Speaking of German names, my former boss had one. It translated to “dry bread”.
I always thought it meant his family was so cheap they wouldn’t even butter their bread.
The name fitted him to a T, which was the name’s first initial.
There’s no need to speculate on why he chose the name ‘Benedict’ - he explained it himself in one of his earliest speeches as Pope.
You know Herr Trockenbrot too?!?!?!
Concerning Darth Ratzi, I guess he will soon be mentioned in the Celebrity Death Pool thread and then we will no longer be Pope. About time too.
That’s what I was going to ask: Sorbs are native to what is now Germany. Serbs are not. Although, that’s in English. In German and in Slavic languages, there might be crossover.
I remember reading that, before he became Pope, he was jokingly (if quietly) referred to around the Vatican as Das Panzerkardinal.
Sorbs=Wends=Vandals=Goths=Prussians=Serbs
Goths were not Germanics.
Well, the Vatican clergy wouldn’t be so cruel as to misgender him, Panzerkardinal notwithstanding, would they? 
So far as I know, Wend was used by German-speaking people to refer to any Slavic-speaking people, including Sorbs and Serbs. In other words, Sorbs and Serbs are two types of Slavs/Wends. So your equation is not correct.
Wends (Old English: Winedas [ˈwi.ne.dɑs]; Old Norse: Vindar ; German: Wenden [ˈvɛn.dn̩], Winden [ˈvɪn.dn̩]; Danish: vendere ; Swedish: vender ; Polish: Wendowie , Czech: Wendové ) is a historical name for Slavs living near Germanic settlement areas. It refers not to a homogeneous people, but to various peoples, tribes or groups depending on where and when it was used.
The meaning of Prussian depends on what stage of history you are talking about. What we now call Old Prussians/Baltic Prussians were Baltic-speaking (not Slavic-speaking) people who lived in the area of what is now Gdansk who were conquered in the early 14th century by the Teutonic Knights. The Baltic Prussian language died out about 500 years later. (Lithuanian and Latvian are modern Baltic languages; they are not Slavic languages.) The Baltic Prussian language was replaced by the Germanic Prussian dialects, in what is now Northeastern Poland and the Kaliningrad exclave of Russia. After World War II, all the speakers of Prussian dialects of German were expelled, and now Polish and Russian are the local languages.
The terms Vandal and Goth were not used with precision in antiquity, and it is unclear whether Goths were a subset of Vandals or whether Goths and Vandals were two separate but related Germanic groups. But they were Germanic-speaking, not Slavic-speaking.
Wikipedia:
Vandalic was the Germanic language spoken by the Vandals during roughly the 3rd to 6th centuries. It was probably closely related to Gothic, and, as such, is traditionally classified as an East Germanic language.
The Vandals spoke a Germanic language who were first described as being in southern Poland and they spread southward towards Mediterranean Europe and North Africa.
Gothic is an extinct East Germanic language that was spoken by the Goths. It is known primarily from the Codex Argenteus , a 6th-century copy of a 4th-century Bible translation, and is the only East Germanic language with a sizeable text corpus. All others, including Burgundian and Vandalic, are known, if at all, only from proper names that survived in historical accounts, and from loanwords in other languages such as Portuguese, Spanish, and French.
The Goths also spoke a Germanic language–the earliest attested Germanic language, in fact. Their origins are not clearly known but they were identified as living in north central Europe before they spread southward and to the east and west.