chan comes from channel
there once was a japanese site 2ちゃんねる (ni-channneru) and people just called it ni-chan, and a few years later 4chan, an english version of it with pictures was born.
Now the suffix -chan is just used for imageboardnames.
Kraut (=cabbage) was used in the past for germans because we used to eat it a lot. I have some Sauerkraut here too.
