This is my first post--I'll go introduce myself in the proper place later.
I can give a definitive answer on this question--which may be the first time in my life that I have been able to do so in an internet forum!
First, the word is--as with most German breed names--a combination of a description of the dog and the German word for dog, "hund". "Hund" is pronounced something like "hoont" (but don't make the "o" so long; think "roof" rather than "moon".) The word "dachs" is pronounced "dox", or close enough, and means "badger". So a Dachshund, or "doxhoont", is a "badger dog".
Now, while the proper pronunciation is close enough to "doxhoont" for you to use that, the term "Dachshund" is seldom used. I've read it several times, but I have NEVER heard any German actually use the term. Ever. They all say "dackel" (pronounced "dockel").
So if you want to go around being pretentious and call the dog what German speakers call it, you say "dockel".
Of course, the best thing is just to go on calling it whatever you called before, and forget about trying to be "authentic".
(Does anyone else remember that SNL sketch where a group of newsroom people were ordering take-out and pronouncing everything in "authentic" Spanish?)
By the way, "Dackel" just means something like "Dachshundie"--you know, a little Dachshund.
Anyway, that's my first post. I hope I haven't scared you all away from future discussion with me.
Jeff