I never heard how in happened, but Mark Twain was apparently quite fluent in German.
Here's a tidbit from "engines" episode 1064;
When Mark Twain's Connecticut Yankee at King Arthur's
Court uttered a bogus magic spell, he used a long German
word:
Konstantinopelitanischerdudelsachspfeifenmachersgesellschaft.
It means an "organization of bagpipe makers from
Constantinople." Should we regard that as six words or just
one?

I like the sound of "dudelsach" much better than "bagpipes".

I like "dudelsach" too. Meanwhile, Twain is the author of one of my favorite rants: "The Awful German Language" (from A Tramp Abroad):

http://www.crossmyt.com/hc/linghebr/awfgrmlg.html

is "doodle sack" really the German word for bag pipe?

and do sack and bag really mean the same thing?

the German word for bag pipe?

I bleeve it is. Sache means thing. Whether Sach means sack I'll have to report back later. Nothing on Dudelsach in my Stilwörterbuch. Whether sack and bag are the same thing you're going to run into lots of regional variation.

"The Awful German Language"

I like the bit about swearing. I asked a foreign exchange student what verdampt meant, working on Twains premise that German swearwords are weak. I don't recall what she said.